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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("这个新写法大大方便了静态属性的表达。")]),s._v(" "),t("div",{staticClass:"language-javascript line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-javascript"}},[t("code",[t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 老写法")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("class")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Foo")]),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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"),t("p",[s._v("另一种方法就是索性将私有方法移出模块，因为模块内部的所有方法都是对外可见的。")]),s._v(" "),t("div",{staticClass:"language-javascript line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-javascript"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("class")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Widget")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("foo")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token parameter"}},[s._v("baz")]),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 function"}},[s._v("bar")]),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 number"}},[s._v("3")]),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("// 输出 false")]),s._v("\n")])]),s._v(" 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"),t("p",[s._v("利用这个特点，可以写出不能独立使用、必须继承后才能使用的类。")]),s._v(" "),t("div",{staticClass:"language-javascript line-numbers-mode"},[t("pre",{pre:!0,attrs:{class:"language-javascript"}},[t("code",[t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("class")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Shape")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token function"}},[s._v("constructor")]),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("{")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("if")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("(")]),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("new")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(".")]),s._v("target 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"),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("Rectangle")]),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 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(" "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("// 正确")]),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("p",[s._v("上面代码中，"),t("code",[s._v("Shape")]),s._v("类不能被实例化，只能用于继承。")]),s._v(" "),t("p",[s._v("注意，在函数外部，使用"),t("code",[s._v("new.target")]),s._v("会报错。")])])}),[],!1,null,null,null);t.default=e.exports}}]);
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