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"),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" obj "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Object")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 等同于 var obj = {}")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("blockquote",[t("p",[s._v("注意，通过"),t("code",[s._v("var obj = new Object()")]),s._v("的写法生成新对象，与字面量的写法"),t("code",[s._v("var obj = {}")]),s._v("是等价的。或者说，后者只是前者的一种简便写法。")])]),s._v(" "),t("p",[t("code",[s._v("Object")]),s._v("构造函数的用法与工具方法很相似，几乎一模一样。使用时，可以接受一个参数，如果该参数是一个对象，则直接返回这个对象；如果是一个原始类型的值，则返回该值对应的包装对象（详见《包装对象》一章）。")]),s._v(" "),t("div",{staticClass:"language- line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-text"}},[t("code",[s._v("var o1 = {a: 1};\nvar o2 = new Object(o1);\no1 === o2 // true\n\nvar obj = new Object(123);\nobj instanceof Number // true\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br")])]),t("p",[s._v("虽然用法相似，但是"),t("code",[s._v("Object(value)")]),s._v("与"),t("code",[s._v("new Object(value)")]),s._v("两者的语义是不同的，"),t("code",[s._v("Object(value)")]),s._v("表示将"),t("code",[s._v("value")]),s._v("转成一个对象，"),t("code",[s._v("new Object(value)")]),s._v("则表示新生成一个对象，它的值是"),t("code",[s._v("value")]),s._v("。")]),s._v(" "),t("h2",{attrs:{id:"_4、object-的静态方法"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_4、object-的静态方法"}},[s._v("#")]),s._v(" 4、Object 的静态方法")]),s._v(" "),t("p",[s._v("所谓“静态方法”，是指"),t("strong",[s._v("部署在"),t("code",[s._v("Object")]),s._v("对象自身")]),s._v("的方法。")]),s._v(" "),t("h3",{attrs:{id:"object-keys"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#object-keys"}},[s._v("#")]),s._v(" Object.keys()")]),s._v(" "),t("p",[t("code",[s._v("Object.keys()")]),s._v("方法和"),t("code",[s._v("Object.getOwnPropertyNames()")]),s._v("方法都用来遍历对象的属性。")]),s._v(" "),t("p",[t("code",[s._v("Object.keys()")]),s._v("方法的参数是一个对象，返回一个数组。该数组的成员都是该对象自身的（而不是继承的）所有"),t("strong",[s._v("属性名")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js 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number"}},[s._v("456")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),s._v("\nObject"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("getOwnPropertyNames")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("obj"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// ['p1','p2']")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// getOwnPropertyNames 中文含义：获取自己的属性名")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br")])]),t("p",[s._v("对于一般的对象来说，"),t("code",[s._v("Object.keys()")]),s._v("和"),t("code",[s._v("Object.getOwnPropertyNames()")]),s._v("返回的结果是一样的。只有涉及不可枚举属性时，才会有不一样的结果。"),t("code",[s._v("Object.keys")]),s._v("方法只返回可枚举的属性（详见《对象属性的描述对象》一章），"),t("code",[s._v("Object.getOwnPropertyNames")]),s._v("方法还返回"),t("strong",[s._v("不可枚举的属性名")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" a "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'hello'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'world'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),s._v("\nObject"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("keys")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("a"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// ['0',‘1’] 如果对象是数组时返回索引字符串")]),s._v("\nObject"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("getOwnPropertyNames")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("a"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// [‘0’,‘1’,'length']")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br")])]),t("p",[s._v("上面代码中，数组的"),t("code",[s._v("length")]),s._v("属性是"),t("strong",[s._v("不可枚举的属性")]),s._v("，所以只出现在"),t("code",[s._v("Object.getOwnPropertyNames")]),s._v("方法的返回结果中。")]),s._v(" "),t("p",[s._v("由于 JavaScript 没有提供计算对象属性个数的方法，所以可以用这两个方法代替。")]),s._v(" "),t("p",[t("strong",[s._v("获取对象属性个数长度")])]),s._v(" "),t("div",{staticClass:"language- line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-text"}},[t("code",[s._v("var obj = {\n p1: 123,\n p2: 456\n};\n\nObject.keys(obj).length // 2\nObject.getOwnPropertyNames(obj).length // 2\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br")])]),t("p",[s._v("一般情况下，几乎总是使用"),t("code",[s._v("Object.keys")]),s._v("方法，遍历对象的属性。")]),s._v(" "),t("h3",{attrs:{id:"object的其他静态方法"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#object的其他静态方法"}},[s._v("#")]),s._v(" Object的其他静态方法")]),s._v(" "),t("p",[s._v("除了上面提到的两个方法，"),t("code",[s._v("Object")]),s._v("还有不少其他静态方法，将在后文逐一详细介绍。")]),s._v(" "),t("h4",{attrs:{id:"_1-对象属性模型的相关方法"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_1-对象属性模型的相关方法"}},[s._v("#")]),s._v(" （1）对象属性模型的相关方法")]),s._v(" "),t("ul",[t("li",[t("code",[s._v("Object.getOwnPropertyDescriptor()")]),s._v("：获取某个属性的描述对象。")]),s._v(" "),t("li",[t("code",[s._v("Object.defineProperty()")]),s._v("：通过描述对象，定义某个属性。")]),s._v(" "),t("li",[t("code",[s._v("Object.defineProperties()")]),s._v("：通过描述对象，定义多个属性。")])]),s._v(" "),t("h4",{attrs:{id:"_2-控制对象状态的方法"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_2-控制对象状态的方法"}},[s._v("#")]),s._v(" （2）控制对象状态的方法")]),s._v(" "),t("ul",[t("li",[t("code",[s._v("Object.preventExtensions()")]),s._v("：防止对象扩展。")]),s._v(" "),t("li",[t("code",[s._v("Object.isExtensible()")]),s._v("：判断对象是否可扩展。")]),s._v(" "),t("li",[t("code",[s._v("Object.seal()")]),s._v("：禁止对象配置。")]),s._v(" "),t("li",[t("code",[s._v("Object.isSealed()")]),s._v("：判断一个对象是否可配置。")]),s._v(" "),t("li",[t("code",[s._v("Object.freeze()")]),s._v("：冻结一个对象。")]),s._v(" "),t("li",[t("code",[s._v("Object.isFrozen()")]),s._v("：判断一个对象是否被冻结。")])]),s._v(" "),t("h4",{attrs:{id:"_3-原型链相关方法"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_3-原型链相关方法"}},[s._v("#")]),s._v(" （3）原型链相关方法")]),s._v(" "),t("ul",[t("li",[t("code",[s._v("Object.create()")]),s._v("：该方法可以指定原型对象和属性，返回一个新的对象。")]),s._v(" "),t("li",[t("code",[s._v("Object.getPrototypeOf()")]),s._v("：获取对象的"),t("code",[s._v("Prototype")]),s._v("对象。")])]),s._v(" "),t("p",[s._v("、")]),s._v(" "),t("p",[s._v("有部分方法为列入此文档，更多方法详情："),t("a",{attrs:{href:"https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object",target:"_blank",rel:"noopener noreferrer"}},[s._v("https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Object"),t("OutboundLink")],1)]),s._v(" "),t("h2",{attrs:{id:"_5、object-的实例方法"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_5、object-的实例方法"}},[s._v("#")]),s._v(" 5、Object 的实例方法")]),s._v(" "),t("p",[s._v("除了静态方法，还有不少方法定义在"),t("code",[s._v("Object.prototype")]),s._v("对象。它们称为实例方法，所有"),t("code",[s._v("Object")]),s._v("的实例对象都继承了这些方法。")]),s._v(" "),t("p",[t("code",[s._v("Object")]),s._v("实例对象的方法，主要有以下六个。")]),s._v(" "),t("ul",[t("li",[t("code",[s._v("Object.prototype.valueOf()")]),s._v("：返回当前对象对应的值。")]),s._v(" "),t("li",[t("code",[s._v("Object.prototype.toString()")]),s._v("：返回当前对象对应的字符串形式。")]),s._v(" "),t("li",[t("code",[s._v("Object.prototype.toLocaleString()")]),s._v("：返回当前对象对应的本地字符串形式。")]),s._v(" "),t("li",[t("code",[s._v("Object.prototype.hasOwnProperty()")]),s._v("：判断某个属性是否为当前对象自身的属性，还是继承自原型对象的属性。")]),s._v(" "),t("li",[t("code",[s._v("Object.prototype.isPrototypeOf()")]),s._v("：判断当前对象是否为另一个对象的原型。")]),s._v(" "),t("li",[t("code",[s._v("Object.prototype.propertyIsEnumerable()")]),s._v("：判断某个属性是否可枚举。")])]),s._v(" "),t("p",[s._v("本节介绍前四个方法，另外两个方法将在后文相关章节介绍。")]),s._v(" 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"),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'toString'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// undefined")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br")])]),t("p",[s._v("上面代码中，"),t("code",[s._v("toString")]),s._v("是"),t("code",[s._v("obj")]),s._v("对象继承的属性，"),t("code",[s._v("Object.getOwnPropertyDescriptor()")]),s._v("无法获取。")]),s._v(" "),t("h2",{attrs:{id:"_3、object-getownpropertynames"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_3、object-getownpropertynames"}},[s._v("#")]),s._v(" 3、Object.getOwnPropertyNames()")]),s._v(" 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hello")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br")])]),t("p",[s._v("上面代码中，对象"),t("code",[s._v("obj")]),s._v("本身不能新增属性，但是可以在它的原型对象上新增属性，就依然能够在"),t("code",[s._v("obj")]),s._v("上读到。")]),s._v(" "),t("p",[s._v("一种解决方案是，把"),t("code",[s._v("obj")]),s._v("的原型也冻结住。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" obj "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Object")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\nObject"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("preventExtensions")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("obj"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" proto "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" Object"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token 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"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// undefined")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br")])]),t("p",[t("strong",[s._v("另外一个局限")]),s._v("是，如果属性值是对象，上面这些方法只能冻结属性指向的对象，而不能冻结对象本身的内容。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" obj "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token literal-property property"}},[s._v("foo")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token literal-property property"}},[s._v("bar")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'b'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),t("span",{pre:!0,attrs:{class:"token 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1、Array构造函数")]),s._v(" "),t("p",[t("code",[s._v("Array")]),s._v("是 JavaScript 的原生对象，同时也是一个构造函数，可以用它生成新的数组。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" arr "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Array")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// Array是原生对象，也是构造函数； 2表示生成2个成员")]),s._v("\narr"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("length "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 2")]),s._v("\narr "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// [ empty x 2 ]")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br")])]),t("p",[s._v("上面代码中，"),t("code",[s._v("Array")]),s._v("构造函数的参数"),t("code",[s._v("2")]),s._v("，表示生成一个两个成员的数组，每个位置都是空值。")]),s._v(" "),t("p",[s._v("如果没有使用"),t("code",[s._v("new")]),s._v("，运行结果也是一样的。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" arr "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Array")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 等同于")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" arr "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("Array")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br")])]),t("p",[t("code",[s._v("Array")]),s._v("构造函数有一个很大的"),t("strong",[s._v("缺陷")]),s._v("，就是不同的参数，会导致它的行为不一致。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 无参数时，返回一个空数组")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Array")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// []")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 单个正整数参数，表示返回的新数组的长度")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Array")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// [ empty ]")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Array")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// [ empty x 2 ]")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 非正整数的数值作为参数，会报错")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Array")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("3.2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// RangeError: Invalid array length")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Array")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("-")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("3")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// RangeError: Invalid array length")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 单个非数值（比如字符串、布尔值、对象等）作为参数，")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 则该参数是返回的新数组的成员")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Array")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'abc'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// ['abc']")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Array")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// [Array[1]]")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 多参数时，所有参数都是返回的新数组的成员")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Array")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// [1, 2]")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Array")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'b'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'c'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// ['a', 'b', 'c']")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br"),t("span",{staticClass:"line-number"},[s._v("10")]),t("br"),t("span",{staticClass:"line-number"},[s._v("11")]),t("br"),t("span",{staticClass:"line-number"},[s._v("12")]),t("br"),t("span",{staticClass:"line-number"},[s._v("13")]),t("br"),t("span",{staticClass:"line-number"},[s._v("14")]),t("br"),t("span",{staticClass:"line-number"},[s._v("15")]),t("br"),t("span",{staticClass:"line-number"},[s._v("16")]),t("br"),t("span",{staticClass:"line-number"},[s._v("17")]),t("br"),t("span",{staticClass:"line-number"},[s._v("18")]),t("br"),t("span",{staticClass:"line-number"},[s._v("19")]),t("br")])]),t("p",[s._v("可以看到，"),t("code",[s._v("Array")]),s._v("作为构造函数，行为很不一致。因此，不建议使用它生成新数组，直接使用数组字面量是更好的做法。")]),s._v(" 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"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// '1|2|3|4‘")]),s._v("\na"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("join")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// '1,2,3,4'")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br")])]),t("p",[s._v("如果数组成员是"),t("code",[s._v("undefined")]),s._v("或"),t("code",[s._v("null")]),s._v("或空位，会被转成空字符串。")]),s._v(" 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function"}},[s._v("call")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("arguments"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br")])]),t("p",[s._v("上面代码的参数都不是数组，但是通过"),t("code",[s._v("call")]),s._v("方法，在它们上面调用"),t("code",[s._v("slice")]),s._v("方法，就可以把它们转为真正的数组。")]),s._v(" "),t("h3",{attrs:{id:"splice-从第几个开始-删除几个-并添加成员-返回被删除成员。"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#splice-从第几个开始-删除几个-并添加成员-返回被删除成员。"}},[s._v("#")]),s._v(" splice() 从第几个开始，删除几个，并添加成员，返回被删除成员。")]),s._v(" "),t("p",[t("code",[s._v("splice")]),s._v("方法用于"),t("strong",[s._v("删除原数组的一部分成员")]),s._v("，"),t("strong",[s._v("并可以在删除的位置添加新的数组成员")]),s._v("，"),t("strong",[s._v("返回值是被删除的元素")]),s._v("。注意，该方法会"),t("strong",[s._v("改变原数组")]),s._v("。")]),s._v(" "),t("blockquote",[t("p",[s._v("也可以不删除成员同时在指定位置添加新成员")])]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[s._v("arr"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("splice")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("start"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" count"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" addElement1"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" addElement2"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("...")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 第几个开始，删除几个，加入的新成员...(非必需）")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br")])]),t("p",[t("code",[s._v("splice")]),s._v("的第一个参数是删除的起始位置（从0开始），第二个参数是被删除的元素个数。如果后面还有更多的参数，则表示这些就是要被插入数组的新元素。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" a "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br")])]),t("p",[s._v("上面代码从原数组2号位置，删除了2个数组成员。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" a "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'b'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'c'")]),t("span",{pre:!0,attrs:{class:"token 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"),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["e", "f"]')]),s._v("\na "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["a", "b", "c", "d", 1, 2]')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br")])]),t("p",[s._v("上面代码从原数组4号位置删除2个成员，并插入了[1 , 2]新成员。")]),s._v(" "),t("p",[s._v("起始位置如果是负数，就表示从倒数位置开始删除。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" a 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"),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("3")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("4")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" a2 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" a"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("splice")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token 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"),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("111")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("sort")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// [10111, 1101, 111]")]),s._v("\n")])]),s._v(" 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]")]),s._v("\n\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 自定义排序")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),t("span",{pre:!0,attrs:{class:"token literal-property property"}},[s._v("day")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'星期日'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),t("span",{pre:!0,attrs:{class:"token literal-property property"}},[s._v("day")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'星期一'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),t("span",{pre:!0,attrs:{class:"token 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punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("return")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("computedDay")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("o1"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("day"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("charAt")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("-")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("computedDay")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("o2"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("day"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("charAt")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("//[{ day: '星期一' }, { day: '星期五' }, { day: '星期日' }]")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("function")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("computedDay")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token parameter"}},[s._v("v")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("return")]),s._v(" v "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("===")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'一'")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("?")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" v "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("===")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'二'")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("?")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" v "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("===")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'三'")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("?")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("3")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" v "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("===")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'四'")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("?")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("4")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" v "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("===")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'五'")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("?")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("5")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" v "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("===")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'六'")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("?")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("6")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("7")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br"),t("span",{staticClass:"line-number"},[s._v("10")]),t("br"),t("span",{staticClass:"line-number"},[s._v("11")]),t("br"),t("span",{staticClass:"line-number"},[s._v("12")]),t("br"),t("span",{staticClass:"line-number"},[s._v("13")]),t("br"),t("span",{staticClass:"line-number"},[s._v("14")]),t("br"),t("span",{staticClass:"line-number"},[s._v("15")]),t("br"),t("span",{staticClass:"line-number"},[s._v("16")]),t("br"),t("span",{staticClass:"line-number"},[s._v("17")]),t("br"),t("span",{staticClass:"line-number"},[s._v("18")]),t("br"),t("span",{staticClass:"line-number"},[s._v("19")]),t("br"),t("span",{staticClass:"line-number"},[s._v("20")]),t("br"),t("span",{staticClass:"line-number"},[s._v("21")]),t("br"),t("span",{staticClass:"line-number"},[s._v("22")]),t("br"),t("span",{staticClass:"line-number"},[s._v("23")]),t("br"),t("span",{staticClass:"line-number"},[s._v("24")]),t("br")])]),t("p",[s._v("注意，"),t("strong",[s._v("自定义的排序函数应该返回数值")]),s._v("，否则不同的浏览器可能有不同的实现，不能保证结果都一致。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// bad")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("4")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("6")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("0")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token 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b"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 返回布尔值，不推荐")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// good")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("4")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("6")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("0")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("6")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("6")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("sort")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token parameter"}},[s._v("a"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" b")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=>")]),s._v(" a "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("-")]),s._v(" b"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 返回数值，推荐")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br")])]),t("p",[s._v("上面代码中，前一种排序算法返回的是布尔值，这是不推荐使用的。后一种是数值，才是更好的写法。")]),s._v(" "),t("h3",{attrs:{id:"map-映射-每个成员-并返回"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#map-映射-每个成员-并返回"}},[s._v("#")]),s._v(" map() 映射 每个成员 并返回")]),s._v(" "),t("p",[t("code",[s._v("map")]),s._v("方法将数组的所有成员依次传入参数函数，然后把每一次的执行结果组成一个新数组返回。"),t("strong",[s._v("不改变原数组")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js 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4]")]),s._v("\n\nnumbers\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// [1, 2, 3]")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br")])]),t("p",[s._v("上面代码中，"),t("code",[s._v("numbers")]),s._v("数组的所有成员依次执行参数函数，运行结果组成一个新数组返回，原数组没有变化。")]),s._v(" 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number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("3")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("4")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("5")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),s._v("\na"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("indexOf")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("3")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 2 3在数组a中第一次出现的位置为2")]),s._v("\na"),t("span",{pre:!0,attrs:{class:"token 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punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'b'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'c'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("indexOf")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// -1 从1位置开始搜索a，没有搜索到")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[s._v("上面代码从1号位置开始搜索字符"),t("code",[s._v("a")]),s._v("，结果为"),t("code",[s._v("-1")]),s._v("，表示没有搜索到。")]),s._v(" "),t("p",[t("strong",[s._v("lastIndexOf()语法")])]),s._v(" "),t("div",{staticClass:"language- line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-text"}},[t("code",[s._v("arr.lastIndexOf(searchElement[, fromIndex = arr.length - 1])\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[t("code",[s._v("lastIndexOf")]),s._v("方法返回"),t("strong",[s._v("给定元素在数组中最后一次出现的位置")]),s._v("，如果没有则返回"),t("code",[s._v("-1")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" a "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("3")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("4")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),s._v("\na"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("lastIndexOf")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("//3 2在数组a中最后一次出现的位置为3")]),s._v("\na"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("lastIndexOf")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("5")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("//-1")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br")])]),t("p",[s._v("注意，这两个方法不能用来搜索"),t("code",[s._v("NaN")]),s._v("的位置，即它们无法确定数组成员是否包含"),t("code",[s._v("NaN")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("NaN")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("indexOf")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("NaN")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// -1")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("NaN")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("lastIndexOf")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("NaN")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// -1")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br")])]),t("p",[s._v("这是因为这两个方法内部，使用严格相等运算符（"),t("code",[s._v("===")]),s._v("）进行比较，而"),t("code",[s._v("NaN")]),s._v("是唯一一个不等于自身的值。")]),s._v(" "),t("h3",{attrs:{id:"链式使用"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#链式使用"}},[s._v("#")]),s._v(" 链式使用")]),s._v(" "),t("p",[s._v("上面这些数组方法之中，有不少返回的还是数组，所以可以链式使用。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" users "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),t("span",{pre:!0,attrs:{class:"token literal-property property"}},[s._v("name")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'tom'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token literal-property property"}},[s._v("email")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'tom@example.com'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),t("span",{pre:!0,attrs:{class:"token literal-property property"}},[s._v("name")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'peter'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token literal-property property"}},[s._v("email")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'peter@example.com'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\nusers\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("map")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("function")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token parameter"}},[s._v("user")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("return")]),s._v(" user"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("email"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 对每个成员进行遍历，使用返回值组成一个新的数组并返回")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("filter")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("function")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token parameter"}},[s._v("email")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 过滤返回值为false的成员，并返回一个过滤掉的新数组")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("return")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("^t")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("test")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("email"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("forEach")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("function")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token parameter"}},[s._v("email")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 遍历数组")]),s._v("\n console"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("log")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("email"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// "tom@example.com"')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br"),t("span",{staticClass:"line-number"},[s._v("10")]),t("br"),t("span",{staticClass:"line-number"},[s._v("11")]),t("br"),t("span",{staticClass:"line-number"},[s._v("12")]),t("br"),t("span",{staticClass:"line-number"},[s._v("13")]),t("br"),t("span",{staticClass:"line-number"},[s._v("14")]),t("br"),t("span",{staticClass:"line-number"},[s._v("15")]),t("br"),t("span",{staticClass:"line-number"},[s._v("16")]),t("br")])]),t("p",[s._v("上面代码中，先产生一个所有 Email 地址组成的数组，然后再过滤出以"),t("code",[s._v("t")]),s._v("开头的 Email 地址，最后将它打印出来。")]),s._v(" "),t("blockquote",[t("p",[s._v("方法的返回值能满足下一个方法的调用，即可使用链式调用。")])]),s._v(" "),t("h2",{attrs:{id:"四、包装对象"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#四、包装对象"}},[s._v("#")]),s._v(" 四、包装对象")]),s._v(" "),t("h2",{attrs:{id:"_1、定义"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_1、定义"}},[s._v("#")]),s._v(" 1、定义")]),s._v(" "),t("p",[s._v("对象是JavaScript语言中最主要的数据类型，三种原始类型的值——数字、字符串、布尔值 在一定条件下，也会自动转为对象，也就是原始类型的"),t("strong",[s._v("包装对象")]),s._v("（wrapper）")]),s._v(" "),t("p",[s._v("所谓“包装对象”，"),t("strong",[s._v("指的是与数字、字符串、布尔值分别相对应的"),t("code",[s._v("Number")]),s._v("、"),t("code",[s._v("String")]),s._v("、"),t("code",[s._v("Boolean")]),s._v("三个原生对象。这三个原生对象可以把原始类型的值变成（包装成）对象")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" v1 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Number")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("123")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" v2 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("String")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'abc'")]),t("span",{pre:!0,attrs:{class:"token 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"),t("span",{pre:!0,attrs:{class:"token literal-property property"}},[s._v("currency")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'CNY'")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// "￥123.00"')]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("123")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("toLocaleString")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'de-DE'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token literal-property property"}},[s._v("style")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'currency'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token literal-property property"}},[s._v("currency")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(":")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'EUR'")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// "123,00 €"')]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("123")]),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br")])]),t("h3",{attrs:{id:"_4-10-string-prototype-match-匹配子串-返回数组-数组带index、input属性"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_4-10-string-prototype-match-匹配子串-返回数组-数组带index、input属性"}},[s._v("#")]),s._v(" 4.10 String.prototype.match() 匹配子串，返回数组（数组带index、input属性）")]),s._v(" "),t("p",[t("code",[s._v("match")]),s._v("方法"),t("strong",[s._v("用于确定原字符串是否匹配某个子字符串，返回一个数组，成员为匹配的第一个字符串")]),s._v("。如果没有找到匹配，则返回"),t("code",[s._v("null")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'cat, bat, sat, 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"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["bat"]')]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('//["bat", index: 3, input: "catbatsatbat", groups: undefined]')]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// index属性为bat首次出现的索引")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'cat, bat, sat, fat'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("match")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'xt'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// null")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br")])]),t("p",[s._v("返回的数组还有**"),t("code",[s._v("index")]),s._v("属性"),t("strong",[s._v("和")]),t("code",[s._v("input")]),s._v("属性**，分别表示匹配字符串"),t("strong",[s._v("开始的位置")]),s._v("和"),t("strong",[s._v("原始字符串")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" matches "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'cat, bat, sat, fat'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("match")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'at'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\nmatches"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("index "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 1 子串首次出现的索引位置")]),s._v("\nmatches"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("input "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// "cat, bat, sat, fat"')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br")])]),t("p",[t("code",[s._v("match")]),s._v("方法还可以使用"),t("strong",[s._v("正则表达式")]),s._v("作为参数，详见《正则表达式》一章。")]),s._v(" "),t("h3",{attrs:{id:"_4-11-string-prototype-search-搜索子串第一次出现的位置-没有则返-1-string-prototype-replace-替换子串-参数二替换参数一-不改变原字符串"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_4-11-string-prototype-search-搜索子串第一次出现的位置-没有则返-1-string-prototype-replace-替换子串-参数二替换参数一-不改变原字符串"}},[s._v("#")]),s._v(" 4.11 String.prototype.search() 搜索子串第一次出现的位置，没有则返-1，String.prototype.replace() 替换子串，参数二替换参数一，不改变原字符串")]),s._v(" "),t("p",[t("code",[s._v("search")]),s._v("方法的用法基本等同于"),t("code",[s._v("match")]),s._v("，但是"),t("strong",[s._v("返回值为匹配的第一个位置。如果没有找到匹配，则返回"),t("code",[s._v("-1")]),s._v("。")])]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'cat, bat, sat, fat'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("search")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'at'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 1")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[t("code",[s._v("search")]),s._v("方法还可以使用正则表达式作为参数，详见《正则表达式》一节。")]),s._v(" "),t("p",[t("code",[s._v("replace")]),s._v("方法"),t("strong",[s._v("用于替换匹配的子字符串")]),s._v("，一般情况下只替换第一个匹配（除非使用带有"),t("code",[s._v("g")]),s._v("修饰符的正则表达式）。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" str "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'aaa'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\nstr"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("replace")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'b'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// "baa" 一般情况只替换第一个，除非带有g的正则')]),s._v("\nstr "),t("span",{pre:!0,attrs:{class:"token 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"),t("h3",{attrs:{id:"_4-12-string-prototype-split-按给定规则分割字符串-返回数组"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_4-12-string-prototype-split-按给定规则分割字符串-返回数组"}},[s._v("#")]),s._v(" 4.12 String.prototype.split() 按给定规则分割字符串，返回数组")]),s._v(" "),t("p",[t("code",[s._v("split")]),s._v("方法"),t("strong",[s._v("按照给定规则分割字符串，返回一个由分割出来的子字符串组成的数组。")])]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a|b|c'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'|'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["a", "b", "c"]')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[s._v("如果分割规则为空字符串，则返回数组的成员是原字符串的每一个字符。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a|b|c'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("''")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["a", "|", "b", "|", "c"]')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[s._v("如果"),t("strong",[s._v("省略参数，则返回数组的唯一成员就是原字符串")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a|b|c'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["a|b|c"]')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[s._v("如果满足分割规则的两个部分紧邻着（即两个分割符中间没有其他字符），则返回数组之中会有一个空字符串。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a||c'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'|'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// ['a', '', 'c']")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[s._v("如果满足分割规则的部分处于字符串的开头或结尾（即它的前面或后面没有其他字符），则返回数组的第一个或最后一个成员是一个空字符串。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'|b|c'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br")])]),t("p",[t("code",[s._v("split")]),s._v("方法还可以接受"),t("strong",[s._v("第二个参数")]),s._v("，"),t("strong",[s._v("限定返回数组的最大成员数（数组长度）")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a|b|c'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'|'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("0")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// []")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a|b|c'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'|'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["a"]')]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a|b|c'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br")])]),t("p",[s._v("上面代码中，不管有几个参数，返回的都是2013年1月1日零点。")]),s._v(" "),t("p",[s._v("最后，各个参数的取值范围如下。")]),s._v(" "),t("ul",[t("li",[s._v("年：使用四位数年份，比如"),t("code",[s._v("2000")]),s._v("。如果写成两位数或个位数，则加上"),t("code",[s._v("1900")]),s._v("，即"),t("code",[s._v("10")]),s._v("代表1910年。如果是负数，表示公元前。")]),s._v(" "),t("li",[s._v("月："),t("strong",[t("code",[s._v("0")]),s._v("表示一月，依次类推，"),t("code",[s._v("11")]),s._v("表示12月")]),s._v("。")]),s._v(" 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"),t("h3",{attrs:{id:"_4-1-date-now-当前时间戳"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_4-1-date-now-当前时间戳"}},[s._v("#")]),s._v(" 4.1 Date.now() 当前时间戳")]),s._v(" "),t("p",[t("code",[s._v("Date.now")]),s._v("方法"),t("strong",[s._v("返回当前时间距离时间零点（1970年1月1日 00:00:00 UTC）的毫秒数（即时间戳）")]),s._v("，相当于 Unix 时间戳乘以1000。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[s._v("Date"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("now")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 1364026285194")]),s._v("\n")])]),s._v(" 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start"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 自动调用valueOf()方法，返回时间戳的减法运算")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br")])]),t("h3",{attrs:{id:"_5-2-to-类方法-返回字符串相关"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_5-2-to-类方法-返回字符串相关"}},[s._v("#")]),s._v(" 5.2 to 类方法（返回字符串相关）")]),s._v(" "),t("h4",{attrs:{id:"_1-date-prototype-tostring-返回一个完整的日期字符串-直接读取实例默认调用此方法"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_1-date-prototype-tostring-返回一个完整的日期字符串-直接读取实例默认调用此方法"}},[s._v("#")]),s._v(" （1）Date.prototype.toString() 返回一个完整的日期字符串（直接读取实例默认调用此方法）")]),s._v(" 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"),t("h4",{attrs:{id:"_2-date-prototype-toutcstring-返回对应的utc时间-世界标准时-比北京时间晚8小时"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_2-date-prototype-toutcstring-返回对应的utc时间-世界标准时-比北京时间晚8小时"}},[s._v("#")]),s._v(" （2）Date.prototype.toUTCString() 返回对应的UTC时间（世界标准时），比北京时间晚8小时")]),s._v(" "),t("p",[t("code",[s._v("toUTCString")]),s._v("方法返回对应的 UTC 时间，也就是比北京时间晚8个小时。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" d "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Date")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2013")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("0")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\nd"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("toUTCString")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// "Mon, 31 Dec 2012 16:00:00 GMT"')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br")])]),t("h4",{attrs:{id:"_3-date-prototype-toisostring-返回对应时间的-iso8601-写法-utc时间"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_3-date-prototype-toisostring-返回对应时间的-iso8601-写法-utc时间"}},[s._v("#")]),s._v(" （3）Date.prototype.toISOString() 返回对应时间的 ISO8601 写法（UTC时间）")]),s._v(" "),t("p",[t("code",[s._v("toISOString")]),s._v("方法返回对应时间的 ISO8601 写法。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" d "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br")])]),t("p",[t("strong",[s._v("注意，"),t("code",[s._v("toISOString")]),s._v("方法返回的总是 UTC 时区的时间。")])]),s._v(" "),t("h4",{attrs:{id:"_4-date-prototype-tojson-返回符合json格式字符串-与toisostring方法的返回结果完全相同。"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_4-date-prototype-tojson-返回符合json格式字符串-与toisostring方法的返回结果完全相同。"}},[s._v("#")]),s._v(" （4）Date.prototype.toJSON() 返回符合JSON格式字符串，与"),t("code",[s._v("toISOString")]),s._v("方法的返回结果完全相同。")]),s._v(" "),t("p",[t("code",[s._v("toJSON")]),s._v("方法返回一个符合 JSON 格式的 ISO 日期字符串，与"),t("code",[s._v("toISOString")]),s._v("方法的返回结果完全相同。")]),s._v(" "),t("div",{staticClass:"language-js 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"),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" d "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Date")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2013")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("0")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\nd"),t("span",{pre:!0,attrs:{class:"token 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"),t("li",[t("code",[s._v("Date.prototype.toLocaleTimeString()")]),s._v("：本地时间（不含年月日）。")])]),s._v(" "),t("p",[s._v("下面是用法实例。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" d "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Date")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2013")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("0")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\nd"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("toLocaleString")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// 中文版浏览器为"2013年1月1日 上午12:00:00"')]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// 英文版浏览器为"1/1/2013 12:00:00 AM"')]),s._v("\n\nd"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("toLocaleDateString")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// 中文版浏览器为"2013年1月1日"')]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// 英文版浏览器为"1/1/2013"')]),s._v("\n\nd"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("toLocaleTimeString")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// 中文版浏览器为"上午12:00:00"')]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// 英文版浏览器为"12:00:00 AM"')]),s._v("\n")])]),s._v(" 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"),t("h3",{attrs:{id:"_5-4-set-类方法"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_5-4-set-类方法"}},[s._v("#")]),s._v(" 5.4 set 类方法")]),s._v(" "),t("p",[t("code",[s._v("Date")]),s._v("对象提供了一系列"),t("code",[s._v("set*")]),s._v("方法，用来设置实例对象的各个方面。")]),s._v(" "),t("ul",[t("li",[t("code",[s._v("setDate(date)")]),s._v("：设置实例对象对应的每个月的几"),t("strong",[s._v("号")]),s._v("（1-31），返回改变后毫秒时间戳。")]),s._v(" "),t("li",[t("code",[s._v("setFullYear(year [, month, date])")]),s._v("：设置四位"),t("strong",[s._v("年份")]),s._v("。")]),s._v(" "),t("li",[t("code",[s._v("setHours(hour [, min, sec, ms])")]),s._v("：设置"),t("strong",[s._v("小时")]),s._v("（0-23）。")]),s._v(" "),t("li",[t("code",[s._v("setMilliseconds()")]),s._v("：设置"),t("strong",[s._v("毫秒")]),s._v("（0-999）。")]),s._v(" "),t("li",[t("code",[s._v("setMinutes(min [, sec, ms])")]),s._v("：设置"),t("strong",[s._v("分钟")]),s._v("（0-59）。")]),s._v(" "),t("li",[t("code",[s._v("setMonth(month [, date])")]),s._v("：设置"),t("strong",[s._v("月份")]),s._v("（0-11）。")]),s._v(" 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br")])]),t("p",[t("code",[s._v("set*")]),s._v("方法的参数都会自动折算。以"),t("code",[s._v("setDate")]),s._v("为例，如果参数超过当月的最大天数，则向下一个月顺延，如果参数是负数，表示从上个月的最后一天开始减去的天数。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" d1 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Date")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'January 6, 2013'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\nd1"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("setDate")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("32")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 1359648000000")]),s._v("\nd1 "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// Fri Feb 01 2013 00:00:00 GMT+0800 (CST)")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" d2 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br")])]),t("p",[t("code",[s._v("**set")]),s._v("类方法和"),t("code",[s._v("get")]),s._v("类方法，可以结合使用，得到相对时间。**")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" d "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token 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punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 将年份设为去年")]),s._v("\nd"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("setFullYear")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("d"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("getFullYear")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("-")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br")])]),t("p",[t("code",[s._v("set*")]),s._v("系列方法除了"),t("code",[s._v("setTime()")]),s._v("，都有对应的 UTC 版本，即"),t("strong",[s._v("设置 UTC 时区的时间")]),s._v("。")]),s._v(" "),t("ul",[t("li",[t("code",[s._v("setUTCDate()")])]),s._v(" "),t("li",[t("code",[s._v("setUTCFullYear()")])]),s._v(" "),t("li",[t("code",[s._v("setUTCHours()")])]),s._v(" "),t("li",[t("code",[s._v("setUTCMilliseconds()")])]),s._v(" "),t("li",[t("code",[s._v("setUTCMinutes()")])]),s._v(" "),t("li",[t("code",[s._v("setUTCMonth()")])]),s._v(" "),t("li",[t("code",[s._v("setUTCSeconds()")])])]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" d "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Date")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'January 6, 2013'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\nd"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("getUTCHours")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 16")]),s._v("\nd"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("setUTCHours")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("22")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 1357423200000")]),s._v("\nd "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// Sun Jan 06 2013 06:00:00 GMT+0800 (CST)")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br")])]),t("p",[s._v("上面代码中，本地时区（东八时区）的1月6日0点0分，是 UTC 时区的前一天下午16点。设为 UTC 时区的22点以后，就变为本地时区的上午6点。")]),s._v(" "),t("h2",{attrs:{id:"十、regexp-对象"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#十、regexp-对象"}},[s._v("#")]),s._v(" 十、RegExp 对象")]),s._v(" "),t("p",[t("code",[s._v("RegExp")]),s._v("对象提供正则表达式的功能。")]),s._v(" "),t("h2",{attrs:{id:"_1、概述-6"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_1、概述-6"}},[s._v("#")]),s._v(" 1、概述")]),s._v(" "),t("p",[t("strong",[s._v("正则表达式（regular expression）是一种表达文本模式（即字符串结构）的方法，有点像字符串的模板，常常用来按照“给定模式”匹配文本")]),s._v("。比如，正则表达式给出一个 Email 地址的模式，然后用它来确定一个字符串是否为 Email 地址。JavaScript 的正则表达式体系是参照 Perl 5 建立的。")]),s._v(" "),t("p",[t("strong",[s._v("新建正则表达式有两种方法：")])]),s._v(" "),t("p",[t("strong",[s._v("一种是使用字面量，以斜杠表示开始和结束。")])]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" regex "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("xyz")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 效率较高，且直观，推荐。")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[t("strong",[s._v("另一种是使用"),t("code",[s._v("RegExp")]),s._v("构造函数。")])]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" regex "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("RegExp")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'xyz'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[s._v("上面两种写法是等价的，都新建了一个内容为"),t("code",[s._v("xyz")]),s._v("的正则表达式对象。它们的主要区别是，第一种方法在引擎编译代码时，就会新建正则表达式，第二种方法在运行时新建正则表达式，所以前者的效率较高。而且，前者比较便利和直观，所以实际应用中，基本上都采用字面量定义正则表达式。")]),s._v(" "),t("p",[t("code",[s._v("RegExp")]),s._v("构造函数还可以接受第二个参数，表示修饰符（详细解释见下文）。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" regex "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("RegExp")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'xyz'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'i'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// i为修饰符")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 等价于")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" regex "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("xyz")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-flags"}},[s._v("i")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n")])]),s._v(" 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"),t("li",[t("code",[s._v("RegExp.prototype.flags")]),s._v("：返回一个字符串，包含了已经设置的所有修饰符，按字母排序。")])]),s._v(" "),t("p",[s._v("上面四个属性都是"),t("strong",[s._v("只读")]),s._v("的。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("abc")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-flags"}},[s._v("igm")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\nr"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("ignoreCase "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// true 是否设置i修饰符")]),s._v("\nr"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("global "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// true 是否设置g修饰符")]),s._v("\nr"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("multiline "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// true 是否设置m修饰符")]),s._v("\nr"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("flags "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 'gim' 字符串，包含设置的所有修饰符，按字母排序")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br")])]),t("p",[s._v("另一类是与"),t("strong",[s._v("修饰符无关的属性")]),s._v("，主要是下面两个。")]),s._v(" "),t("ul",[t("li",[t("code",[s._v("RegExp.prototype.lastIndex")]),s._v("：返回一个整数，表示下一次开始搜索的位置。该属性可读写，但是只在进行连续搜索时有意义，详细介绍请看后文。")]),s._v(" "),t("li",[t("code",[s._v("RegExp.prototype.source")]),s._v("：返回正则表达式的字符串形式（不包括反斜杠），该属性只读。")])]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" 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"),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("x")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-flags"}},[s._v("g")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 带有g全局匹配修饰符")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" s "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br"),t("span",{staticClass:"line-number"},[s._v("10")]),t("br"),t("span",{staticClass:"line-number"},[s._v("11")]),t("br")])]),t("p",[s._v("上面代码的正则表达式使用了"),t("code",[s._v("g")]),s._v("修饰符，表示是全局搜索，会有多个结果。接着，三次使用"),t("code",[s._v("test")]),s._v("方法，每一次开始搜索的位置都是上一次匹配的后一个位置。")]),s._v(" "),t("p",[s._v("带有"),t("code",[s._v("g")]),s._v("修饰符时，可以通过正则对象的"),t("code",[s._v("lastIndex")]),s._v("属性指定开始搜索的位置。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("x")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-flags"}},[s._v("g")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" s "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'_x_x'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\nr"),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br")])]),t("p",[s._v("上面代码指定从字符串的第五个位置开始搜索，这个位置为空，所以返回"),t("code",[s._v("false")]),s._v("。同时，"),t("code",[s._v("lastIndex")]),s._v("属性重置为"),t("code",[s._v("0")]),s._v("，所以第二次执行"),t("code",[s._v("r.test(s)")]),s._v("会返回"),t("code",[s._v("true")]),s._v("。")]),s._v(" "),t("p",[t("strong",[s._v("注意")]),s._v("，"),t("strong",[s._v("带有"),t("code",[s._v("g")]),s._v("修饰符时，正则表达式内部会记住上一次的"),t("code",[s._v("lastIndex")]),s._v("属性")]),s._v("，这时不应该更换所要匹配的字符串，否则会有一些难以察觉的错误。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("bb")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-flags"}},[s._v("g")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\nr"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("test")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'bb'")]),t("span",{pre:!0,attrs:{class:"token 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"),t("p",[t("code",[s._v("lastIndex")]),s._v("属性只对同一个正则表达式有效，所以下面这样写是错误的。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" count "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("0")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("while")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("a")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-flags"}},[s._v("g")])]),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br")])]),t("h3",{attrs:{id:"_3-2-regexp-prototype-exec-返回匹配结果-如匹配则返回一个数组-成员是匹配到的子字符串-否则返回null"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_3-2-regexp-prototype-exec-返回匹配结果-如匹配则返回一个数组-成员是匹配到的子字符串-否则返回null"}},[s._v("#")]),s._v(" 3.2 RegExp.prototype.exec() 返回匹配结果，如匹配则返回一个数组，成员是匹配到的子字符串，否则返回null")]),s._v(" "),t("p",[s._v("正则实例对象的"),t("code",[s._v("exec")]),s._v("方法，用来"),t("strong",[s._v("返回匹配结果。如果发现匹配，就返回一个数组，成员是匹配成功的子字符串，否则返回"),t("code",[s._v("null")]),s._v("。")])]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" s "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'_x_x'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r1 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("x")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r2 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("y")]),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br")])]),t("p",[s._v("上面代码中，正则对象"),t("code",[s._v("r1")]),s._v("匹配成功，返回一个数组，成员是匹配结果；正则对象"),t("code",[s._v("r2")]),s._v("匹配失败，返回"),t("code",[s._v("null")]),s._v("。")]),s._v(" "),t("p",[t("strong",[s._v("如果正则表示式包含圆括号（即含有“组匹配”），则返回的数组会包括多个成员")]),s._v("。第一个成员是整个匹配成功的结果，后面的成员就是圆括号对应的匹配成功的组。也就是说，第二个成员对应第一个括号，第三个成员对应第二个括号，以此类推。整个数组的"),t("code",[s._v("length")]),s._v("属性等于组匹配的数量再加1。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" s 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line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("a(b+)a")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" arr "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" r"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("exec")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'_abbba_aba_'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\narr "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["abbba", "bbb"] // 第一个成员是整个匹配的结果，第二个成员是圆括号匹配的结果')]),s._v("\n\narr"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("index "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 1 表示是在1位置开始匹配成功的")]),s._v("\narr"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("input "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// "_abbba_aba_"')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br")])]),t("p",[s._v("上面代码中的"),t("code",[s._v("index")]),s._v("属性等于1，是因为从原字符串的第二个位置开始匹配成功。")]),s._v(" "),t("p",[s._v("如果正则表达式加上"),t("code",[s._v("g")]),s._v("修饰符，则可以使用多次"),t("code",[s._v("exec")]),s._v("方法，下一次搜索的位置从上一次匹配成功结束的位置开始。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" reg "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("a")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-flags"}},[s._v("g")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 带'g'修饰符")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" str "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'abc_abc_abc'")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r1 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" reg"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("exec")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("str"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\nr1 "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["a"]')]),s._v("\nr1"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("index "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 0 在0位置匹配成功")]),s._v("\nreg"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("lastIndex "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 1 下一次匹配开始位置为1")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r2 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" reg"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("exec")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("str"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\nr2 "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["a"]')]),s._v("\nr2"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("index "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 4 在4位置匹配成功")]),s._v("\nreg"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("lastIndex "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 5 下一次匹配开始位置为5")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r3 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" reg"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("exec")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("str"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\nr3 "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["a"]')]),s._v("\nr3"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("index "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 8 在8位置匹配成功")]),s._v("\nreg"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("lastIndex "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 9 下一次匹配开始位置为9")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r4 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" reg"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("exec")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("str"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token 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"),t("p",[s._v("利用"),t("code",[s._v("g")]),s._v("修饰符允许多次匹配的特点，可以用一个循环完成全部匹配。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" reg "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("a")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-flags"}},[s._v("g")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" str "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br"),t("span",{staticClass:"line-number"},[s._v("10")]),t("br"),t("span",{staticClass:"line-number"},[s._v("11")]),t("br")])]),t("p",[s._v("上面代码中，只要"),t("code",[s._v("exec")]),s._v("方法不返回"),t("code",[s._v("null")]),s._v("，就会一直循环下去，每次输出匹配的位置和匹配的文本。")]),s._v(" "),t("p",[s._v("正则实例对象的"),t("code",[s._v("lastIndex")]),s._v("属性不仅可读，还可写。设置了"),t("code",[s._v("g")]),s._v("修饰符的时候，只要手动设置了"),t("code",[s._v("lastIndex")]),s._v("的值，就会从指定位置开始匹配。")]),s._v(" "),t("h2",{attrs:{id:"_4、字符串的实例方法"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_4、字符串的实例方法"}},[s._v("#")]),s._v(" 4、字符串的实例方法")]),s._v(" "),t("p",[t("strong",[s._v("字符串的实例方法之中，有4种与正则表达式有关。")])]),s._v(" "),t("ul",[t("li",[t("code",[s._v("String.prototype.match()")]),s._v("：返回一个数组，成员是所有匹配的子字符串。")]),s._v(" "),t("li",[t("code",[s._v("String.prototype.search()")]),s._v("：按照给定的正则表达式进行搜索，返回一个整数，表示匹配开始的位置。")]),s._v(" "),t("li",[t("code",[s._v("String.prototype.replace()")]),s._v("：按照给定的正则表达式进行替换，返回替换后的字符串。")]),s._v(" "),t("li",[t("code",[s._v("String.prototype.split()")]),s._v("：按照给定规则进行字符串分割，返回一个数组，包含分割后的各个成员。")])]),s._v(" "),t("h3",{attrs:{id:"_4-1-string-prototype-match-匹配-返回匹配结果数组或null"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_4-1-string-prototype-match-匹配-返回匹配结果数组或null"}},[s._v("#")]),s._v(" 4.1 String.prototype.match() 匹配，返回匹配结果数组或null")]),s._v(" "),t("p",[s._v("字符串实例对象的"),t("code",[s._v("match")]),s._v("方法"),t("strong",[s._v("对字符串进行正则匹配，返回匹配结果")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" s "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'_x_x'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r1 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br")])]),t("p",[s._v("从上面代码可以看到，字符串的"),t("code",[s._v("match")]),s._v("方法与正则对象的"),t("code",[s._v("exec")]),s._v("方法非常类似：匹配成功返回一个数组，匹配失败返回"),t("code",[s._v("null")]),s._v("。")]),s._v(" "),t("p",[s._v("如果正则表达式带有"),t("code",[s._v("g")]),s._v("修饰符，则该方法与正则对象的"),t("code",[s._v("exec")]),s._v("方法行为不同，会一次性返回所有匹配成功的结果。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" s "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'abba'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("a")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-flags"}},[s._v("g")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\ns"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("match")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("r"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["a", "a"] 带g修饰符，会返回全部结果到数组成员')]),s._v("\nr"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("exec")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("s"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["a"] 正则实例的exec方法只返回一个')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br")])]),t("p",[s._v("设置"),t("strong",[s._v("正则表达式的"),t("code",[s._v("lastIndex")]),s._v("属性，对"),t("code",[s._v("match")]),s._v("方法无效")]),s._v("，匹配总是从字符串的第一个字符开始。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" r "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source 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'b']")]),s._v("\nr"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("lastIndex "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 0")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br")])]),t("p",[s._v("上面代码表示，设置正则对象的"),t("code",[s._v("lastIndex")]),s._v("属性是无效的。")]),s._v(" "),t("h3",{attrs:{id:"_4-2-string-prototype-search-返回第一个满足匹配条件的位置-不满足则返-1"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_4-2-string-prototype-search-返回第一个满足匹配条件的位置-不满足则返-1"}},[s._v("#")]),s._v(" 4.2 String.prototype.search() 返回第一个满足匹配条件的位置，不满足则返-1")]),s._v(" "),t("p",[s._v("字符串对象的"),t("code",[s._v("search")]),s._v("方法，"),t("strong",[s._v("返回第一个满足条件的匹配结果在整个字符串中的位置")]),s._v("。"),t("strong",[s._v("如果没有任何匹配，则返回"),t("code",[s._v("-1")]),s._v("。")])]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'_x_x'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("search")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("x")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 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不带g修饰符，只匹配并替换第一个')]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'aaa'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("replace")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("a")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-flags"}},[s._v("g")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'b'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// "bbb" 带g修饰符，匹配全局，并替换全部匹配到的值')]),s._v("\n")])]),s._v(" 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"),t("p",[t("code",[s._v("replace")]),s._v("方法的第"),t("strong",[s._v("二个参数还可以是一个函数，将每一个匹配内容替换为函数返回值")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'3 and 5'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("replace")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("[0-9]+")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-flags"}},[s._v("g")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("function")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token parameter"}},[s._v("match")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("return")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("*")]),s._v(" match"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// match参数是匹配到的内容")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// "6 and 10"')]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" a "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'The quick brown fox jumped over the lazy dog.'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" pattern "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("quick|brown|lazy")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-flags"}},[s._v("ig")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\na"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br"),t("span",{staticClass:"line-number"},[s._v("10")]),t("br"),t("span",{staticClass:"line-number"},[s._v("11")]),t("br"),t("span",{staticClass:"line-number"},[s._v("12")]),t("br")])]),t("p",[s._v("作为"),t("code",[s._v("replace")]),s._v("方法第二个参数的替换函数，可以接受多个参数。其中，第一个参数是捕捉到的内容，第二个参数是捕捉到的组匹配（"),t("strong",[s._v("有多少个组匹配，就有多少个对应的参数")]),s._v("）。此外，最后还可以添加两个参数，倒数第二个参数是捕捉到的内容在整个字符串中的位置（比如从第五个位置开始），最后一个参数是原字符串。下面是一个网页模板替换的例子。")]),s._v(" 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$1"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" $2"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" $3"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" $4"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" index"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" str")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("return")]),s._v(" $1 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("+")]),s._v(" $2 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("+")]),s._v(" $3 "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("+")]),s._v(" prices"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),s._v("$2"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("+")]),s._v(" $4"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// "<span id="p1">$1.99</span><span id="p2">$9.99</span><span id="p3">$5.00</span>"')]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 说明：")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// match 整个匹配到的内容：<span id="p*"></span>')]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 以下参数分别是匹配到的组内容，有多少组就对应多少个参数")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// $1 <span id="')]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// $2 p1~p3")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// $3 ">')]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// $4 </span>")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 后面还可以接受两个参数：")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 倒数第二个是：捕捉到的内容(即match的内容)在整个字符串中的位置")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 最后一个是：原字符串")]),s._v("\n\n")])]),s._v(" 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"),t("h3",{attrs:{id:"_4-4-string-prototype-split-按给定规则分割字符串-返回数组"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_4-4-string-prototype-split-按给定规则分割字符串-返回数组"}},[s._v("#")]),s._v(" 4.4 String.prototype.split() 按给定规则分割字符串，返回数组")]),s._v(" "),t("p",[s._v("字符串对象的"),t("code",[s._v("split")]),s._v("方法"),t("strong",[s._v("按照正则规则分割字符串，返回一个由分割后的各个部分组成的数组。")])]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[s._v("str"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),s._v("separator"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),s._v("limit"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[s._v("该方法接受"),t("strong",[s._v("两个参数")]),s._v("，第一个参数是正则表达式，表示分隔规则，第二个参数是返回数组的最大成员数（数组长度）。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 非正则分隔")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a, b,c, d'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("','")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// [ 'a', ' b', 'c', ' d' ]")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 正则分隔，去除多余的空格")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a, b,c, d'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v(", *")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// [ 'a', 'b', 'c', 'd' ]")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 指定返回数组的最大成员（数组长度）")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a, b,c, d'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v(", *")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("2")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'b'")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br"),t("span",{staticClass:"line-number"},[s._v("10")]),t("br"),t("span",{staticClass:"line-number"},[s._v("11")]),t("br")])]),t("p",[s._v("上面代码使用正则表达式，去除了子字符串的逗号后面的空格。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 例一")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'aaa*a*'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("a*")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// [ '', '*', '*' ] 分隔符，即被过滤的符号，")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 例二")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'aaa**a*'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("a*")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["", "*", "*", "*"]')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br")])]),t("p",[s._v("上面代码的分割规则是0次或多次的"),t("code",[s._v("a")]),s._v("，由于正则默认是贪婪匹配，所以例一的第一个分隔符是"),t("code",[s._v("aaa")]),s._v("，第二个分割符是"),t("code",[s._v("a")]),s._v("，将字符串分成三个部分，包含开始处的空字符串。例二的第一个分隔符是"),t("code",[s._v("aaa")]),s._v("，第二个分隔符是0个"),t("code",[s._v("a")]),s._v("（即空字符），第三个分隔符是"),t("code",[s._v("a")]),s._v("，所以将字符串分成四个部分。")]),s._v(" "),t("p",[s._v("如果正则表达式"),t("strong",[s._v("带有括号")]),s._v("，则括号匹配的部分也会作为数组成员返回。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'aaa*a*'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("split")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("(a*)")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// [ '', 'aaa', '*', 'a', '*' ]")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br")])]),t("p",[s._v("上面代码的正则表达式使用了括号，第一个组匹配是"),t("code",[s._v("aaa")]),s._v("，第二个组匹配是"),t("code",[s._v("a")]),s._v("，它们都作为数组成员返回。")]),s._v(" "),t("h2",{attrs:{id:"_5、匹配规则"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_5、匹配规则"}},[s._v("#")]),s._v(" 5、匹配规则")]),s._v(" "),t("p",[s._v("搭配菜鸟教程一起学习更容易理解："),t("a",{attrs:{href:"https://www.runoob.com/regexp/regexp-tutorial.html",target:"_blank",rel:"noopener noreferrer"}},[s._v("https://www.runoob.com/regexp/regexp-tutorial.html"),t("OutboundLink")],1)]),s._v(" "),t("p",[s._v("正则表达式在线测试与常用正则表达式："),t("a",{attrs:{href:"http://c.runoob.com/front-end/854",target:"_blank",rel:"noopener noreferrer"}},[s._v("http://c.runoob.com/front-end/854"),t("OutboundLink")],1)]),s._v(" "),t("p",[s._v("正则表达式的规则很复杂，下面一一介绍这些规则。")]),s._v(" "),t("h3",{attrs:{id:"_5-1-字面量字符和元字符"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_5-1-字面量字符和元字符"}},[s._v("#")]),s._v(" 5.1 字面量字符和元字符")]),s._v(" "),t("p",[t("strong",[s._v("大部分字符在正则表达式中，就是字面的含义，比如"),t("code",[s._v("/a/")]),s._v("匹配"),t("code",[s._v("a")]),s._v("，"),t("code",[s._v("/b/")]),s._v("匹配"),t("code",[s._v("b")])]),s._v("。如果在正则表达式之中，某个字符只表示它字面的含义（就像前面的"),t("code",[s._v("a")]),s._v("和"),t("code",[s._v("b")]),s._v("），那么它们就叫做“字面量字符”（literal characters）。")]),s._v(" "),t("div",{staticClass:"language- line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-text"}},[t("code",[s._v("/dog/.test('old dog') // true\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[s._v("上面代码中正则表达式的"),t("code",[s._v("dog")]),s._v("，就是字面量字符，所以"),t("code",[s._v("/dog/")]),s._v("匹配"),t("code",[s._v("old dog")]),s._v("，因为它就表示"),t("code",[s._v("d")]),s._v("、"),t("code",[s._v("o")]),s._v("、"),t("code",[s._v("g")]),s._v("三个字母连在一起。")]),s._v(" "),t("p",[s._v("除了字面量字符以外，还"),t("strong",[s._v("有一部分字符有特殊含义，不代表字面的意思。它们叫做“元字符”")]),s._v("（metacharacters），主要有以下几个。")]),s._v(" "),t("h4",{attrs:{id:"_1-点字符-类似通配"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_1-点字符-类似通配"}},[s._v("#")]),s._v(" （1）点字符（.) 类似通配")]),s._v(" "),t("p",[s._v("点字符（"),t("code",[s._v(".")]),s._v("）"),t("strong",[s._v("匹配除回车（"),t("code",[s._v("\\r")]),s._v("）、换行("),t("code",[s._v("\\n")]),s._v(") 、行分隔符（"),t("code",[s._v("\\u2028")]),s._v("）和段分隔符（"),t("code",[s._v("\\u2029")]),s._v("）以外的任何单个字符")]),s._v("。注意，对于码点大于"),t("code",[s._v("0xFFFF")]),s._v("字符，点字符不能正确匹配，会认为这是两个字符。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br")])]),t("p",[s._v("上面代码中，"),t("code",[s._v("c.t")]),s._v("匹配"),t("code",[s._v("c")]),s._v("和"),t("code",[s._v("t")]),s._v("之间包含任意一个字符的情况，只要这三个字符在同一行，比如"),t("code",[s._v("cat")]),s._v("、"),t("code",[s._v("c2t")]),s._v("、"),t("code",[s._v("c-t")]),s._v("等等，但是不匹配"),t("code",[s._v("coot")]),s._v("。")]),s._v(" "),t("h4",{attrs:{id:"_2-位置字符-开始位置和结束位置"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_2-位置字符-开始位置和结束位置"}},[s._v("#")]),s._v(" （2）位置字符(^) ($) 开始位置和结束位置")]),s._v(" "),t("p",[s._v("位置字符用来提示字符所处的位置，主要有两个字符。")]),s._v(" "),t("ul",[t("li",[t("strong",[t("code",[s._v("^")]),s._v(" 表示字符串的开始位置")])]),s._v(" "),t("li",[t("strong",[t("code",[s._v("$")]),s._v(" 表示字符串的结束位置")])])]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// test必须出现在开始位置")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("^")]),s._v("test"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("test")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'test123'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// true")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// test必须出现在结束位置")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("/")]),s._v("test$"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("test")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'new test'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// true")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 从开始位置到结束位置只有test")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("^")]),s._v("test$"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token 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false")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br")])]),t("h4",{attrs:{id:"_3-选择符-表示-或关系"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_3-选择符-表示-或关系"}},[s._v("#")]),s._v(" （3）选择符（"),t("code",[s._v("|")]),s._v("） 表示''或关系''")]),s._v(" "),t("p",[s._v("竖线符号（"),t("code",[s._v("|")]),s._v("）在正则表达式中表示“"),t("strong",[s._v("或关系")]),s._v("”（OR），即"),t("code",[s._v("cat|dog")]),s._v("表示匹配"),t("code",[s._v("cat")]),s._v("或"),t("code",[s._v("dog")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("11|22")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("test")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'911'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// true")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[s._v("上面代码中，正则表达式指定必须匹配"),t("code",[s._v("11")]),s._v("或"),t("code",[s._v("22")]),s._v("。")]),s._v(" "),t("p",[s._v("多个选择符可以联合使用。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 匹配fred、barney、betty之中的一个")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("/")]),s._v("fred"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("|")]),s._v("barney"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("|")]),s._v("betty"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("/")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br")])]),t("p",[s._v("选择符会包括它前后的多个字符，比如"),t("code",[s._v("/ab|cd/")]),s._v("指的是匹配"),t("code",[s._v("ab")]),s._v("或者"),t("code",[s._v("cd")]),s._v("，而不是指匹配"),t("code",[s._v("b")]),s._v("或者"),t("code",[s._v("c")]),s._v("。如果想修改这个行为，可以使用圆括号。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("a( |\\t)b")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("test")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'a\\tb'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// true")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[s._v("上面代码指的是，"),t("code",[s._v("a")]),s._v("和"),t("code",[s._v("b")]),s._v("之间有一个空格或者一个制表符。")]),s._v(" "),t("p",[s._v("其他的元字符还包括"),t("code",[s._v("\\")]),s._v("、"),t("code",[s._v("\\*")]),s._v("、"),t("code",[s._v("+")]),s._v("、"),t("code",[s._v("?")]),s._v("、"),t("code",[s._v("()")]),s._v("、"),t("code",[s._v("[]")]),s._v("、"),t("code",[s._v("{}")]),s._v("等，将在下文解释。")]),s._v(" "),t("h3",{attrs:{id:"_5-2-转义符-反斜杠"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_5-2-转义符-反斜杠"}},[s._v("#")]),s._v(" 5.2 转义符（\\ 反斜杠）")]),s._v(" "),t("p",[s._v("正则表达式中那些有特殊含义的元字符，如果要匹配它们本身，就需要在它们前面要加上反斜杠。比如要匹配"),t("code",[s._v("+")]),s._v("，就要写成"),t("code",[s._v("\\+")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("1+1")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("test")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'1+1'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// false")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),s._v("\\"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("+")]),t("span",{pre:!0,attrs:{class:"token number"}},[s._v("1")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("test")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'1+1'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// true")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br")])]),t("p",[s._v("上面代码中，第一个正则表达式之所以不匹配，因为加号是元字符，不代表自身。第二个正则表达式使用反斜杠对加号转义，就能匹配成功。")]),s._v(" "),t("p",[s._v("正则表达式中，"),t("strong",[s._v("需要反斜杠转义的，一共有12个字符")]),s._v("："),t("code",[s._v("^")]),s._v("、"),t("code",[s._v(".")]),s._v("、"),t("code",[s._v("[")]),s._v("、"),t("code",[s._v("$")]),s._v("、"),t("code",[s._v("(")]),s._v("、"),t("code",[s._v(")")]),s._v("、"),t("code",[s._v("|")]),s._v("、"),t("code",[s._v("*")]),s._v("、"),t("code",[s._v("+")]),s._v("、"),t("code",[s._v("?")]),s._v("、"),t("code",[s._v("{")]),s._v("和"),t("code",[s._v("\\")]),s._v("。需要特别注意的是，如果使用"),t("code",[s._v("RegExp")]),s._v("方法生成正则对象，转义需要使用两个斜杠，因为字符串内部会先转义一次。")]),s._v(" 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"),t("p",[s._v("预定义模式指的是"),t("strong",[s._v("某些常见模式的简写方式")]),s._v("。")]),s._v(" "),t("ul",[t("li",[t("code",[s._v("\\d")]),s._v(" 匹配0-9之间的任一数字，相当于"),t("code",[s._v("[0-9]")]),s._v("。"),t("strong",[s._v("(数字)")])]),s._v(" "),t("li",[t("code",[s._v("\\D")]),s._v(" 匹配所有0-9以外的字符，相当于"),t("code",[s._v("[^0-9]")]),s._v("。"),t("strong",[s._v("(非数字)")])]),s._v(" "),t("li",[t("code",[s._v("\\w")]),s._v(" 匹配任意的字母、数字和下划线，相当于"),t("code",[s._v("[A-Za-z0-9_]")]),s._v("。"),t("strong",[s._v("(字母、数字、下划线)")])]),s._v(" "),t("li",[t("code",[s._v("\\W")]),s._v(" 除所有字母、数字和下划线以外的字符，相当于"),t("code",[s._v("[^A-Za-z0-9_]")]),s._v("。"),t("strong",[s._v("(非：字母、数字、下划线)")])]),s._v(" "),t("li",[t("code",[s._v("\\s")]),s._v(" 匹配空格（包括换行符、制表符、空格符等），相等于"),t("code",[s._v("[ \\t\\r\\n\\v\\f]")]),s._v("。"),t("strong",[s._v("(空格)")])]),s._v(" "),t("li",[t("code",[s._v("\\S")]),s._v(" 匹配非空格的字符，相当于"),t("code",[s._v("[^ \\t\\r\\n\\v\\f]")]),s._v("。"),t("strong",[s._v("(非空格)")])]),s._v(" "),t("li",[t("code",[s._v("\\b")]),s._v(" 匹配词的边界。"),t("strong",[s._v("(单词边界)")])]),s._v(" "),t("li",[t("code",[s._v("\\B")]),s._v(" 匹配非词边界，即在词的内部。"),t("strong",[s._v("(非单词边界)")])])]),s._v(" "),t("p",[s._v("下面是一些例子。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// \\s 的例子")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("/")]),s._v("\\s\\w"),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("*")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("exec")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'hello world'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// [" 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br")])]),t("p",[s._v("上面的代码中，字符串结尾处有一个换行符。如果不加"),t("code",[s._v("m")]),s._v("修饰符，匹配不成功，因为字符串的结尾不是"),t("code",[s._v("world")]),s._v("；加上以后，"),t("code",[s._v("$")]),s._v("可以匹配行尾。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("^b")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-flags"}},[s._v("m")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("test")]),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br")])]),t("p",[s._v("上面代码使用带"),t("code",[s._v("g")]),s._v("修饰符的正则表达式，结果"),t("code",[s._v("match")]),s._v("方法只捕获了匹配整个表达式的部分。这时必须使用正则表达式的"),t("code",[s._v("exec")]),s._v("方法，配合循环，才能读到每一轮匹配的组捕获。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" str "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'abcabc'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" reg "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br")])]),t("p",[s._v("上面代码中，"),t("code",[s._v("\\1")]),s._v("指向外层括号，"),t("code",[s._v("\\2")]),s._v("指向内层括号。")]),s._v(" "),t("p",[s._v("组匹配非常有用，下面是一个匹配网页标签的例子。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" tagName "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("<([^>]+)>[^<]*<\\/\\1>")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\ntagName"),t("span",{pre:!0,attrs:{class:"token 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"),t("p",[s._v("上面代码略加修改，就能捕获带有属性的标签。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" html "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'<b class=\"hello\">Hello</b><i>world</i>'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" tag "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("<(\\w+)([^>]*)>(.*?)<\\/\\1>")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token 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"),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br"),t("span",{staticClass:"line-number"},[s._v("10")]),t("br"),t("span",{staticClass:"line-number"},[s._v("11")]),t("br"),t("span",{staticClass:"line-number"},[s._v("12")]),t("br"),t("span",{staticClass:"line-number"},[s._v("13")]),t("br"),t("span",{staticClass:"line-number"},[s._v("14")]),t("br")])]),t("h4",{attrs:{id:"_2-非捕获组"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_2-非捕获组"}},[s._v("#")]),s._v(" （2）非捕获组")]),s._v(" "),t("p",[t("code",[s._v("(?:x)")]),s._v("称为非捕获组（Non-capturing group），表示"),t("strong",[s._v("不返回该组匹配的内容，即匹配的结果中不计入这个括号")]),s._v("。")]),s._v(" "),t("p",[s._v("非捕获组的作用请考虑这样一个场景，假定需要匹配"),t("code",[s._v("foo")]),s._v("或者"),t("code",[s._v("foofoo")]),s._v("，正则表达式就应该写成"),t("code",[s._v("/(foo){1, 2}/")]),s._v("，但是这样会占用一个组匹配。这时，就可以使用非捕获组，将正则表达式改为"),t("code",[s._v("/(?:foo){1, 2}/")]),s._v("，它的作用与前一个正则是一样的，但是不会单独输出括号内部的内容。")]),s._v(" "),t("p",[s._v("请看下面的例子。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" m "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'abc'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("match")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("(?:.)b(.)")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\nm "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["abc", "c"]')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br")])]),t("p",[s._v("上面代码中的模式，一共使用了两个括号。其中第一个括号是非捕获组，所以最后返回的结果中没有第一个括号，只有第二个括号匹配的内容。")]),s._v(" "),t("p",[s._v("下面是用来分解网址的正则表达式。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 正常匹配")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" url "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("(http|ftp):\\/\\/([^/\\r\\n]+)(\\/[^\\r\\n]*)?")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\nurl"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("exec")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'http://google.com/'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["http://google.com/", "http", "google.com", "/"]')]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 非捕获组匹配")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" url "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("(?:http|ftp):\\/\\/([^/\\r\\n]+)(\\/[^\\r\\n]*)?")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n\nurl"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("exec")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'http://google.com/'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["http://google.com/", "google.com", "/"]')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br"),t("span",{staticClass:"line-number"},[s._v("3")]),t("br"),t("span",{staticClass:"line-number"},[s._v("4")]),t("br"),t("span",{staticClass:"line-number"},[s._v("5")]),t("br"),t("span",{staticClass:"line-number"},[s._v("6")]),t("br"),t("span",{staticClass:"line-number"},[s._v("7")]),t("br"),t("span",{staticClass:"line-number"},[s._v("8")]),t("br"),t("span",{staticClass:"line-number"},[s._v("9")]),t("br"),t("span",{staticClass:"line-number"},[s._v("10")]),t("br"),t("span",{staticClass:"line-number"},[s._v("11")]),t("br")])]),t("p",[s._v("上面的代码中，前一个正则表达式是正常匹配，第一个括号返回网络协议；后一个正则表达式是非捕获匹配，返回结果中不包括网络协议。")]),s._v(" "),t("h4",{attrs:{id:"_3-先行断言"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_3-先行断言"}},[s._v("#")]),s._v(" （3）先行断言")]),s._v(" "),t("p",[t("code",[s._v("x(?=y)")]),s._v("称为先行断言（Positive look-ahead）"),t("strong",[s._v("，"),t("code",[s._v("x")]),s._v("只有在"),t("code",[s._v("y")]),s._v("前面才匹配，"),t("code",[s._v("y")]),s._v("不会被计入返回结果")]),s._v("。比如，要匹配后面跟着百分号的数字，可以写成"),t("code",[s._v("/\\d+(?=%)/")]),s._v("。")]),s._v(" "),t("p",[s._v("“先行断言”中，括号里的部分是不会返回的。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" m "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'abc'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("match")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("b(?=c)")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\nm "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["b"]')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br")])]),t("p",[s._v("上面的代码使用了先行断言，"),t("code",[s._v("b")]),s._v("在"),t("code",[s._v("c")]),s._v("前面所以被匹配，但是括号对应的"),t("code",[s._v("c")]),s._v("不会被返回。")]),s._v(" "),t("h4",{attrs:{id:"_4-先行否定断言"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_4-先行否定断言"}},[s._v("#")]),s._v(" （4）先行否定断言")]),s._v(" "),t("p",[t("code",[s._v("x(?!y)")]),s._v("称为先行否定断言（Negative look-ahead），"),t("strong",[t("code",[s._v("x")]),s._v("只有不在"),t("code",[s._v("y")]),s._v("前面才匹配，"),t("code",[s._v("y")]),s._v("不会被计入返回结果")]),s._v("。比如，要匹配后面跟的不是百分号的数字，就要写成"),t("code",[s._v("/\\d+(?!%)/")]),s._v("。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("\\d+(?!\\.)")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("exec")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'3.14'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v('// ["14"]')]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br")])]),t("p",[s._v("上面代码中，正则表达式指定，只有不在小数点前面的数字才会被匹配，因此返回的结果就是"),t("code",[s._v("14")]),s._v("。")]),s._v(" "),t("p",[s._v("“先行否定断言”中，括号里的部分是不会返回的。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("var")]),s._v(" m "),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("=")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v("'abd'")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("match")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token regex"}},[t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")]),t("span",{pre:!0,attrs:{class:"token regex-source language-regex"}},[s._v("b(?!c)")]),t("span",{pre:!0,attrs:{class:"token regex-delimiter"}},[s._v("/")])]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(")")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(";")]),s._v("\nm "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// ['b']")]),s._v("\n")])]),s._v(" "),t("div",{staticClass:"line-numbers-wrapper"},[t("span",{staticClass:"line-number"},[s._v("1")]),t("br"),t("span",{staticClass:"line-number"},[s._v("2")]),t("br")])]),t("p",[s._v("上面的代码使用了先行否定断言，"),t("code",[s._v("b")]),s._v("不在"),t("code",[s._v("c")]),s._v("前面所以被匹配，而且括号对应的"),t("code",[s._v("d")]),s._v("不会被返回。")]),s._v(" "),t("h2",{attrs:{id:"十一、json对象"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#十一、json对象"}},[s._v("#")]),s._v(" 十一、JSON对象")]),s._v(" "),t("h2",{attrs:{id:"_1、json-格式"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#_1、json-格式"}},[s._v("#")]),s._v(" 1、JSON 格式")]),s._v(" "),t("p",[s._v("JSON 格式（JavaScript Object Notation 的缩写）是一种用于数据交换的文本格式，2001年由 Douglas Crockford 提出，目的是取代繁琐笨重的 XML 格式。")]),s._v(" "),t("p",[s._v("相比 XML 格式，JSON 格式有两个显著的优点：书写简单，一目了然；符合 JavaScript 原生语法，可以由解释引擎直接处理，不用另外添加解析代码。所以，JSON 迅速被接受，已经成为各大网站交换数据的标准格式，并被写入标准。")]),s._v(" "),t("p",[t("strong",[s._v("每个 JSON 对象就是一个值，可能是一个数组或对象，也可能是一个原始类型的值")]),s._v("。总之，"),t("strong",[s._v("只能是一个值")]),s._v("，不能是两个或更多的值。")]),s._v(" "),t("p",[s._v("JSON 对值的类型和格式有严格的"),t("strong",[s._v("规定")]),s._v("。")]),s._v(" "),t("blockquote",[t("ol",[t("li",[s._v("复合类型的值只能是数组或对象，不能是函数、正则表达式对象、日期对象。")]),s._v(" "),t("li",[s._v("原始类型的值只有四种：字符串、数值（必须以十进制表示）、布尔值和"),t("code",[s._v("null")]),s._v("（不能使用"),t("code",[s._v("NaN")]),s._v(", "),t("code",[s._v("Infinity")]),s._v(", "),t("code",[s._v("-Infinity")]),s._v("和"),t("code",[s._v("undefined")]),s._v("）。")]),s._v(" "),t("li",[s._v("字符串必须使用双引号表示，不能使用单引号。")]),s._v(" "),t("li",[s._v("对象的键名必须放在双引号里面。")]),s._v(" "),t("li",[s._v("数组或对象最后一个成员的后面，不能加逗号。")])])]),s._v(" "),t("p",[s._v("以下都是合法的 JSON。")]),s._v(" "),t("div",{staticClass:"language-js line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-js"}},[t("code",[t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("[")]),t("span",{pre:!0,attrs:{class:"token string"}},[s._v('"one"')]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v('"two"')]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string"}},[s._v('"three"')]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("]")]),s._v("\n\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token string-property property"}},[s._v('"one"')]),t("span",{pre:!0,attrs:{class:"token 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