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key")]),t._v(" "),s("p",[s("strong",[t._v("key 帮助 React 识别哪些元素改变了")]),t._v("，比如被添加或删除。因此你应当给数组中的每一个元素赋予一个确定的标识。")]),t._v(" "),s("p",[t._v("一个元素的 key 最好是这个元素在列表中拥有的"),s("strong",[t._v("一个独一无二的字符串")]),t._v("。"),s("strong",[t._v("通常，我们使用数据中的 id 来作为元素的 key")])]),t._v(" "),s("div",{staticClass:"language-jsx line-numbers-mode"},[s("pre",{pre:!0,attrs:{class:"language-jsx"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("const")]),t._v(" todoItems "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" todos"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("map")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token parameter"}},[t._v("todo")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token 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嵌套了太多层级，那可能就是你"),s("a",{attrs:{href:"https://zh-hans.reactjs.org/docs/components-and-props.html#extracting-components",target:"_blank",rel:"noopener noreferrer"}},[t._v("提取组件"),s("OutboundLink")],1),t._v("的一个好时机。")])])}),[],!1,null,null,null);s.default=e.exports}}]);
    2.