{"id":1875,"date":"2025-09-23T14:03:34","date_gmt":"2025-09-23T06:03:34","guid":{"rendered":"https:\/\/womeifei.cn\/?p=1875"},"modified":"2025-09-24T22:49:05","modified_gmt":"2025-09-24T14:49:05","slug":"react-hooks","status":"publish","type":"post","link":"https:\/\/womeifei.cn\/index.php\/2025\/09\/23\/react-hooks\/","title":{"rendered":"React Hooks"},"content":{"rendered":"\n

\u53ca\u65f6\u66f4\u65b0\u4e2d……<\/p>\n\n\n\n

1.useState\u72b6\u6001\u94a9\u5b50<\/h2>\n\n\n\n

1.1\u4f7f\u7528\u573a\u666f<\/h3>\n\n\n\n

\u5f53\u4e00\u4e2a\u6570\u636e\u9700\u8981\u54cd\u5e94\u5f0f\u5448\u73b0\u5230\u9875\u9762\u4e0a\u65f6\uff0c\u9700\u8981\u4f7f\u7528 useState<\/code> \u72b6\u6001\u58f0\u660e\u94a9\u5b50\u6765\u544a\u77e5 React \u76d1\u542c\u6570\u636e\uff0c\u4ece\u800c\u5b9e\u73b0\u9875\u9762\u7684\u6570\u636e\u52a8\u6001\u66f4\u65b0<\/p>\n\n\n\n

1.2\u4f7f\u7528\u793a\u4f8b<\/h3>\n\n\n\n
import { useState } from 'react'\n\nconst myComponent = () => {\n  const [count, setCount] = useState<number>(0)\n  const handleClick1 = () => setCount(count + 1)       \/\/ \u7b49\u6548\n  const handleClick2 = () => setCount(pre => pre + 1)  \/\/ \u7b49\u6548\n  return <button onClick={handleClick1}>count: {count}<\/button>\n}<\/code><\/pre>\n\n\n\n
\u58f0\u660e\u65b9\u6cd5\u4e3a const [val, setVal] = useState<T>(default)<\/code><\/strong> \uff0c\u8be5\u65b9\u6cd5\u4f1a\u4f7f\u7528\u6cdb\u578b T<\/code> \u4f5c\u4e3a\u9650\u5236\uff0c default<\/code> \u4f5c\u4e3a\u521d\u59cb\u503c\uff0c\u8fd4\u56de\u7684 val<\/code> \u4e3a\u6570\u636e\u672c\u8eab\uff0c\u800c setVal<\/code> \u4e3a\u66f4\u65b0\u6570\u636e\u7684\u65b9\u6cd5<\/p>\n\n\n\n
\u5f53\u72b6\u6001\u6539\u53d8\u65f6\uff0c\u76f4\u63a5\u6539\u52a8 val<\/code> \u662f\u65e0\u6548\u7684\uff0c\u9700\u8981\u628a\u65b0\u7684 val<\/code> \u901a\u8fc7 setVal<\/code> \u4f5c\u4e3a\u53c2\u6570\u53d1\u9001\uff0c\u4ece\u800c\u8fbe\u5230\u6539\u53d8\u6570\u636e\u7684\u6548\u679c<\/p>\n\n\n\n
setVal<\/code> \u51fd\u6570\u4e5f\u53ef\u4ee5\u63a5\u53d7\u4e00\u4e2a\u51fd\u6570 func<\/code> \u4f5c\u4e3a\u53c2\u6570\uff0cReact \u4f1a\u8c03\u7528 func<\/code> \u5e76\u5c06\u539f\u6709\u7684 val<\/code> \u4f5c\u4e3a\u53c2\u6570\u4f20\u9012\uff0c\u5c06 func<\/code> \u7684\u8fd4\u56de\u503c\u4f5c\u4e3a\u65b0\u7684\u6570\u636e<\/p>\n\n\n\n
1.3\u6ce8\u610f\u4e8b\u9879<\/h3>\n\n\n\n
1.3.1 \u4fee\u6539\u72b6\u6001\u4f1a\u5bfc\u81f4\u7ec4\u4ef6\u91cd\u65b0\u6267\u884c<\/h4>\n\n\n\n
\u5f53\u7ec4\u4ef6\u7684\u4e00\u4e2a\u72b6\u6001\u88ab\u4fee\u6539\u65f6\uff0cReact \u4f1a\u8c03\u7528\u65b9\u6cd5\u91cd\u65b0\u6e32\u67d3\u7ec4\u4ef6<\/p>\n\n\n\n
import { useState } from 'react'\n\nconst myComponent = () => {\n  const [count, setCount] = useState<number>(0)\n  console.log('render')\n  const handleClick = () => setCount(count + 1)\n  return <button onClick={handleClick}>count: {count}<\/button>\n}<\/code><\/pre>\n\n\n\n
\u6bcf\u5f53\u6309\u94ae\u88ab\u70b9\u51fb\u65f6\uff0c\u72b6\u6001\u66f4\u6539\uff0c\u7ec4\u4ef6\u91cd\u65b0\u6e32\u67d3\uff0c\u63a7\u5236\u53f0\u8f93\u51fa render<\/code> \uff0c\u6309\u94ae\u5185\u90e8\u7684\u6570\u636e\u53d8\u66f4<\/p>\n\n\n\n
\u82e5 handleClick<\/code> \u51fd\u6570\u672a\u4f7f\u7528 setCount<\/code> \u800c\u662f\u76f4\u63a5\u4fee\u6539 count<\/code> \u672c\u8eab\uff0c\u5219\u5f53\u70b9\u51fb\u6309\u94ae\u65f6\uff0c\u4e0d\u4f1a\u89e6\u53d1\u91cd\u65b0\u6e32\u67d3\uff0c\u63a7\u5236\u53f0\u4e0d\u4f1a\u518d\u6b21\u8f93\u51fa render<\/code> \uff0c\u6309\u94ae\u5185\u90e8\u7684\u6570\u636e\u4e5f\u4e0d\u4f1a\u53d8\u66f4\uff0c\u4f46 count<\/code> \u53d8\u91cf\u672c\u8eab\u662f\u5df2\u7ecf\u6539\u53d8\u4e86\u7684<\/p>\n\n\n\n
1.3.2 \u4fee\u6539\u72b6\u6001\u662f\u5f02\u6b65\u64cd\u4f5c<\/h4>\n\n\n\n
setVal<\/code> \u51fd\u6570\u4f1a\u5c06\u5185\u5bb9\u5b58\u653e\u4e8e\u5fae\u961f\u5217\u4e2d\uff0c\u5728\u540c\u6b65\u4ee3\u7801\u6267\u884c\u7ed3\u675f\u540e\u518d\u6267\u884c<\/p>\n\n\n\n
\u540c\u65f6\uff0c setVal<\/code> \u51fd\u6570\u4f1a\u81ea\u52a8\u5408\u5e76\uff0c\u591a\u6b21\u8c03\u7528\u4e00\u6b21\u6267\u884c\uff0c\u6267\u884c\u540e\u518d\u8fdb\u884c\u91cd\u65b0\u6e32\u67d3\uff0c\u4ee5\u9632\u591a\u6b21\u4e0d\u5fc5\u8981\u7684\u91cd\u65b0\u6e32\u67d3<\/p>\n\n\n\n
import { useState } from 'react'\n\nconst myComponent = () => {\n  const [count, setCount] = useState<number>(0)\n  const handleClick = () => {\n    setCount(count + 1)\n    setCount(count + 1)\n    setCount(count + 1)\n    console.log(count)\n  }\n  return <button onClick={handleClick}>count: {count}<\/button>\n}<\/code><\/pre>\n\n\n\n
\u5982\u4e0a\u4ee3\u7801\uff0c\u5728\u6309\u94ae\u70b9\u51fb\u65f6\uff0c\u867d\u7136\u6267\u884c\u4e86\u4e09\u6b21 setCount<\/code> \uff0c\u4f46\u7531\u4e8e JavaScript<\/code> \u7684\u9884\u5148\u8ba1\u7b97\uff0c\u82e5\u672c\u6b21 count<\/code> \u4e3a 0<\/code> \uff0c\u5219\u7b49\u6548\u4e8e\u6267\u884c\u4e86\u4e09\u6b21 setCount(1)<\/code> \uff0c\u6545\u6bcf\u6b21\u70b9\u51fb\u6309\u94ae\uff0c count<\/code> \u7684\u503c\u53ea\u4f1a\u81ea\u589e 1<\/code> \uff0c\u800c\u975e\u9884\u60f3\u4e2d\u7684\u81ea\u589e 3<\/code><\/p>\n\n\n\n
\u540c\u65f6\uff0c\u7531\u4e8e setVal<\/code> \u51fd\u6570\u7684\u5f02\u6b65\u6027\uff0c console.log(count)<\/code> \u5728\u63a7\u5236\u53f0\u7684\u8f93\u51fa\u4e5f\u662f\u5148\u524d\u800c\u975e\u66f4\u65b0\u540e\u7684 count<\/code> \u503c<\/p>\n\n\n\n
\u5bf9\u4e8e\u4e0a\u8ff0\u4ee3\u7801\uff0c\u7b26\u5408\u9884\u671f\u7684\u89e3\u51b3\u65b9\u5f0f\u662f\u4f7f\u7528 setVal<\/code> \u51fd\u6570\u7684\u56de\u8c03\u51fd\u6570\u53c2\u6570<\/p>\n\n\n\n
import { useState } from 'react'\n\nconst myComponent = () => {\n  const [count, setCount] = useState<number>(0)\n  const handleClick = () => {\n    setCount(pre => pre + 1)\n    setCount(pre => pre + 1)\n    setCount(pre => {\n      console.log(pre + 1)\n      return pre + 1\n    })\n  }\n  return <button onClick={handleClick}>count: {count}<\/button>\n}<\/code><\/pre>\n\n\n\n
\u7531\u4e8e setVal<\/code> \u51fd\u6570\u7684\u56de\u8c03\u51fd\u6570\u53c2\u6570\u4e5f\u662f\u5f02\u6b65\u8c03\u7528\u7684\uff0c\u56de\u8c03\u51fd\u6570\u53c2\u6570\u63a5\u6536\u53c2\u6570 pre<\/code> \u65f6\uff0c\u72b6\u6001 count<\/code> \u5df2\u88ab\u4e0a\u4e00\u6b21\u72b6\u6001\u4fee\u6539\u51fd\u6570\u4fee\u6539\u5b8c\u6bd5\uff0c\u6545\u53d6\u5230\u7684\u662f\u65b0\u503c\uff0c\u7406\u6240\u5f53\u7136\u5730\uff0c\u63a7\u5236\u53f0\u8f93\u51fa\u7b49\u64cd\u4f5c\u4e5f\u4f1a\u8f93\u51fa\u6b63\u786e\u7684\u65b0\u503c<\/p>\n\n\n\n
1.3.3 \u72b6\u6001\u5177\u6709\u7f13\u5b58\u80fd\u529b<\/h4>\n\n\n\n
\u6bcf\u4e00\u4e2a\u72b6\u6001\u90fd\u88ab\u7f13\u5b58\u5728 Fiber \u8282\u70b9\u7684 memoizedState<\/code> \u5c5e\u6027\u4e2d\uff0c\u800c\u975e\u7ec4\u4ef6\u5185\u90e8<\/p>\n\n\n\n
\u4e0d\u7136\u6bcf\u6b21\u7ec4\u4ef6\u91cd\u65b0\u6e32\u67d3\u65f6 useState<\/code> \u94a9\u5b50\u63a5\u6536\u5230\u7684\u9ed8\u8ba4\u503c\u5c31\u4f1a\u8986\u76d6\u539f\u6709\u72b6\u6001\uff0c\u6b64\u94a9\u5b50\u5c31\u65e0\u4efb\u4f55\u610f\u4e49\u4e86<\/p>\n\n\n\n
2.useEffect\u5916\u90e8\u4f5c\u7528\u94a9\u5b50<\/h2>\n\n\n\n
2.1\u4f7f\u7528\u573a\u666f<\/h3>\n\n\n\n
\u5f53\u9700\u8981\u5728\u7ec4\u4ef6\u6e32\u67d3\u540e\u6267\u884c\u4e00\u4e9b\u526f\u4f5c\u7528\u64cd\u4f5c\u65f6\uff08\u5982\u8bf7\u6c42\u6570\u636e\u3001DOM \u64cd\u4f5c\u3001\u8ba2\u9605\u4e8b\u4ef6\u3001\u5b9a\u65f6\u5668\u7b49\uff09\uff0c\u4f7f\u7528 useEffect<\/code> \u6765\u58f0\u660e\u526f\u4f5c\u7528\u903b\u8f91<\/p>\n\n\n\n
\u5e38\u89c1\u7684\u4f7f\u7528\u573a\u666f\u5305\u62ec\uff1a<\/p>\n\n\n\n
    \n
  • \u6570\u636e\u83b7\u53d6\uff08API\u8bf7\u6c42\uff09<\/li>\n\n\n\n
  • \u8ba2\u9605\u5916\u90e8\u6570\u636e\u6e90<\/li>\n\n\n\n
  • \u624b\u52a8\u64cd\u4f5cDOM\u5143\u7d20<\/li>\n\n\n\n
  • \u8bbe\u7f6e\u5b9a\u65f6\u5668\u6216\u8ba1\u65f6\u5668<\/li>\n\n\n\n
  • \u8bb0\u5f55\u65e5\u5fd7\u6216\u5206\u6790\u6570\u636e<\/li>\n\n\n\n
  • \u4e0e\u7b2c\u4e09\u65b9\u5e93\u96c6\u6210<\/li>\n<\/ul>\n\n\n\n
    2.2\u4f7f\u7528\u793a\u4f8b<\/h3>\n\n\n\n
    import { useState, useEffect } from 'react'\n\nconst MyComponent = () => {\n  const [count, setCount] = useState<number>(0)\n  \n  \/\/ \u7ec4\u4ef6\u6302\u8f7d\u65f6\u548ccount\u53d8\u5316\u65f6\u6267\u884c\n  useEffect(() => {\n    document.title = `\u70b9\u51fb\u4e86 ${count} \u6b21`\n    console.log('\u526f\u4f5c\u7528\u6267\u884c')\n  }, [count]) \/\/ \u4f9d\u8d56\u6570\u7ec4\u4e2d\u5305\u542bcount\n  \n  return (\n    <button onClick={() => setCount(count + 1)}>\n      \u70b9\u51fb\u6b21\u6570: {count}\n    <\/button>\n  )\n}<\/code><\/pre>\n\n\n\n
    useEffect<\/code> \u63a5\u53d7\u4e24\u4e2a\u53c2\u6570\uff1a\u4e00\u4e2a\u526f\u4f5c\u7528\u51fd\u6570 effect<\/code> \u548c\u4e00\u4e2a\u4f9d\u8d56\u6570\u7ec4 deps<\/code> \u3002\u5f53 deps<\/code> \u4e2d\u7684\u6570\u636e\u53d8\u5316\u65f6\uff0c\u526f\u4f5c\u7528\u51fd\u6570\u4f1a\u88ab\u91cd\u65b0\u6267\u884c<\/p>\n\n\n\n
    \u4f9d\u8d56\u6570\u7ec4\u7684\u4e0d\u540c\u60c5\u51b5\uff1a<\/p>\n\n\n\n
      \n
    • useEffect(fn, [])<\/code> \uff1a\u4ec5\u5728\u7ec4\u4ef6\u6302\u8f7d\u65f6\u6267\u884c\u4e00\u6b21\uff0c\u7ec4\u4ef6\u5378\u8f7d\u65f6\u6267\u884c\u6e05\u7406\u51fd\u6570<\/li>\n\n\n\n
    • useEffect(fn, [dep1, dep2])<\/code> \uff1a\u5728\u7ec4\u4ef6\u6302\u8f7d\u548c\u4f9d\u8d56\u9879\u53d8\u5316\u65f6\u6267\u884c<\/li>\n\n\n\n
    • useEffect(fn)<\/code> \uff1a\u5728\u6bcf\u6b21\u6e32\u67d3\u540e\u90fd\u6267\u884c\uff08\u4e0d\u63a8\u8350\uff0c\u53ef\u80fd\u5bfc\u81f4\u65e0\u9650\u5faa\u73af\uff09<\/li>\n<\/ul>\n\n\n\n
      2.3\u6ce8\u610f\u4e8b\u9879<\/h3>\n\n\n\n
      2.3.1\u6e05\u7406\u526f\u4f5c\u7528<\/h4>\n\n\n\n
      \u526f\u4f5c\u7528\u51fd\u6570\u53ef\u4ee5\u8fd4\u56de\u4e00\u4e2a\u6e05\u7406\u51fd\u6570 cleanup<\/code> \uff0c\u5f53\u7ec4\u4ef6\u5378\u8f7d\u6216\u4f9d\u8d56\u66f4\u65b0\u65f6\uff0cReact \u4f1a\u6267\u884c\u6e05\u7406\u903b\u8f91<\/p>\n\n\n\n
      MyComponent.tsx<\/p>\n\n\n\n
      import { useState, useEffect } from 'react'\n\nexport const MyComponent = () => {\n    const [isOnline, setIsOnline] = useState<boolean>(navigator.onLine)\n\n    useEffect(() => {\n        \/\/ \u8bbe\u7f6e\u4e8b\u4ef6\u76d1\u542c\u5668\n        const handleOnline = () => setIsOnline(true)\n        const handleOffline = () => setIsOnline(false)\n\n        window.addEventListener('online', handleOnline)\n        window.addEventListener('offline', handleOffline)\n\n        console.log('\u6dfb\u52a0\u4e86\u4e8b\u4ef6\u76d1\u542c')\n\n        \/\/ \u8fd4\u56de\u6e05\u7406\u51fd\u6570\n        \/\/ 1.\u4e8b\u4ef6\u76d1\u542c\u5668\n        \/\/ 2.\u5b9a\u65f6\u5668\n        \/\/ 3.\u8ba2\u9605\n        \/\/ 4.\u624b\u52a8DOM\u64cd\u4f5c\n        \/\/ 5.WebSocket\u8fde\u63a5\n        return () => {\n            window.removeEventListener('online', handleOnline)\n            window.removeEventListener('offline', handleOffline)\n            console.log('\u79fb\u9664\u4e86\u4e8b\u4ef6\u76d1\u542c')\n        }\n    }, [])\n    \/\/ \u7a7a\u4f9d\u8d56\u6570\u7ec4\uff0c\u4ec5\u5728\u7ec4\u4ef6\u6302\u8f7d\u548c\u5378\u8f7d\u65f6\u6267\u884c\n    \/\/ \u76d1\u542c\u5668\u7684\u751f\u547d\u5468\u671f = \u7ec4\u4ef6\u7684\u751f\u547d\u5468\u671f\n\n    return (\n        <div>\n            \u5f53\u524d\u7f51\u7edc\u72b6\u6001: {isOnline ? '\u5728\u7ebf' : '\u79bb\u7ebf'}\n        <\/div>\n    )\n}<\/code><\/pre>\n\n\n\n
      App.tsx<\/p>\n\n\n\n
      import { useState } from 'react'\nimport { MyComponent } from '.\/components\/Example'\n\nconst App = () => {\n  const [showComponent, setShowComponent] = useState(true)\n\n  return (\n    <div>\n      <button onClick={() => setShowComponent(!showComponent)}>\n        {showComponent ? '\u5378\u8f7d\u7ec4\u4ef6' : '\u6302\u8f7d\u7ec4\u4ef6'}\n      <\/button>\n\n      {showComponent && <MyComponent \/>}\n    <\/div>\n  )\n}\n\nexport default App<\/code><\/pre>\n\n\n\n
      \u5e38\u89c1\u7684\u6e05\u7406\u903b\u8f91\u6709\u53d6\u6d88\u8ba2\u9605\u3001\u6e05\u9664\u5b9a\u65f6\u5668\u7b49\uff0c\u907f\u514d\u5185\u5b58\u6cc4\u6f0f\u6216\u91cd\u590d\u6ce8\u518c<\/p>\n\n\n\n
      2.3.2\u4f9d\u8d56\u9879\u7f3a\u5931\u95ee\u9898<\/h4>\n\n\n\n
      \u5982\u679c\u5728\u526f\u4f5c\u7528\u4e2d\u4f7f\u7528\u4e86\u7ec4\u4ef6\u5185\u7684\u53d8\u91cf\u6216\u72b6\u6001\uff0c\u4f46\u6ca1\u6709\u5c06\u5176\u6dfb\u52a0\u5230\u4f9d\u8d56\u6570\u7ec4\u4e2d\uff0c\u53ef\u80fd\u4f1a\u5bfc\u81f4\u95ed\u5305\u9677\u9631\uff0c\u4f7f\u7528\u7684\u662f\u65e7\u503c\u800c\u975e\u6700\u65b0\u503c<\/p>\n\n\n\n
      2.3.3 \u907f\u514d\u65e0\u9650\u5faa\u73af<\/h4>\n\n\n\n
      \u5982\u679c\u5728\u526f\u4f5c\u7528\u4e2d\u66f4\u65b0\u4e86\u4f9d\u8d56\u6570\u7ec4\u4e2d\u5305\u542b\u7684\u72b6\u6001\uff0c\u4f1a\u5bfc\u81f4\u65e0\u9650\u5faa\u73af\uff1a\u526f\u4f5c\u7528\u6267\u884c \u2192 \u72b6\u6001\u66f4\u65b0 \u2192 \u7ec4\u4ef6\u91cd\u65b0\u6e32\u67d3 \u2192 \u526f\u4f5c\u7528\u518d\u6b21\u6267\u884c<\/p>\n\n\n\n
      \n
      3.useContext\u4e0a\u4e0b\u6587\u94a9\u5b50<\/h2>\n\n\n\n
      3.1\u4f7f\u7528\u573a\u666f<\/h3>\n\n\n\n
      \u7528\u4e8e\u5728\u7ec4\u4ef6\u6811\u4e2d\u8de8\u5c42\u7ea7\u4f20\u9012\u6570\u636e\uff0c\u800c\u4e0d\u5fc5\u5c42\u5c42\u901a\u8fc7 props \u4f20\u9012\u3002\u9002\u7528\u4e8e\u4ee5\u4e0b\u573a\u666f\uff1a<\/p>\n\n\n\n
        \n
      • \u5168\u5c40\u4e3b\u9898\u8bbe\u7f6e\uff08\u660e\/\u6697\u6a21\u5f0f\uff09<\/li>\n\n\n\n
      • \u7528\u6237\u8ba4\u8bc1\u4fe1\u606f\u5171\u4eab<\/li>\n\n\n\n
      • \u8bed\u8a00\u504f\u597d\u8bbe\u7f6e<\/li>\n\n\n\n
      • \u5168\u5c40\u72b6\u6001\u7ba1\u7406<\/li>\n\n\n\n
      • \u8def\u7531\u4fe1\u606f\u5171\u4eab<\/li>\n<\/ul>\n\n\n\n
        3.2\u4f7f\u7528\u793a\u4f8b<\/h3>\n\n\n\n
        import { createContext, useContext, useState } from 'react'\n\n\/\/ \u521b\u5efa\u4e0a\u4e0b\u6587\nconst ThemeContext = createContext<'light' | 'dark'>('light')\n\n\/\/ \u7236\u7ec4\u4ef6\u63d0\u4f9b\u4e0a\u4e0b\u6587\nconst App = () => {\n  const [theme, setTheme] = useState<'light' | 'dark'>('light')\n  \n  const toggleTheme = () => {\n    setTheme(prevTheme => prevTheme === 'light' ? 'dark' : 'light')\n  }\n  \n  return (\n    <ThemeContext.Provider value={theme}>\n      <div>\n        <button onClick={toggleTheme}>\u5207\u6362\u4e3b\u9898<\/button>\n        <ThemedButton \/>\n      <\/div>\n    <\/ThemeContext.Provider>\n  )\n}\n\n\/\/ \u5b50\u7ec4\u4ef6\u6d88\u8d39\u4e0a\u4e0b\u6587\nconst ThemedButton = () => {\n  const theme = useContext(ThemeContext)\n  \n  const style = {\n    background: theme === 'dark' ? '#333' : '#fff',\n    color: theme === 'dark' ? '#fff' : '#333',\n    padding: '10px',\n    borderRadius: '4px'\n  }\n  \n  return (\n    <button style={style}>\n      \u5f53\u524d\u4e3b\u9898: {theme}\n    <\/button>\n  )\n}<\/code><\/pre>\n\n\n\n
        \u4f7f\u7528 Context \u9700\u8981\u4e09\u4e2a\u6b65\u9aa4\uff1a<\/p>\n\n\n\n
          \n
        1. \u901a\u8fc7 createContext<\/code> \u521b\u5efa\u4e0a\u4e0b\u6587\uff0c\u53ef\u4ee5\u63d0\u4f9b\u9ed8\u8ba4\u503c<\/li>\n\n\n\n
        2. \u7236\u7ec4\u4ef6\u4f7f\u7528 Context.Provider<\/code> \u63d0\u4f9b\u6570\u636e\uff0c\u901a\u8fc7 value \u5c5e\u6027\u4f20\u9012<\/li>\n\n\n\n
        3. \u5b50\u7ec4\u4ef6\u901a\u8fc7 useContext<\/code> \u94a9\u5b50\u83b7\u53d6\u4e0a\u4e0b\u6587\u6570\u636e<\/li>\n<\/ol>\n\n\n\n
          3.3\u6ce8\u610f\u4e8b\u9879<\/h3>\n\n\n\n
          3.3.1\u6027\u80fd\u8003\u8651<\/h4>\n\n\n\n
          \u5f53 Provider \u7684 value \u53d8\u5316\u65f6\uff0c\u6240\u6709\u6d88\u8d39\u8be5 Context \u7684\u7ec4\u4ef6\u90fd\u4f1a\u91cd\u65b0\u6e32\u67d3\uff0c\u5373\u4f7f\u5b83\u4eec\u6ca1\u6709\u4f7f\u7528\u53d8\u5316\u7684\u90e8\u5206\u3002\u53ef\u4ee5\u901a\u8fc7\u62c6\u5206 Context \u6216\u4f7f\u7528 memo \u4f18\u5316<\/p>\n\n\n\n
          3.3.2 \u9ed8\u8ba4\u503c\u7684\u5c40\u9650\u6027<\/h4>\n\n\n\n
          Context \u7684\u9ed8\u8ba4\u503c\u53ea\u6709\u5728\u7ec4\u4ef6\u6811\u4e2d\u6ca1\u6709\u5339\u914d\u7684 Provider \u65f6\u624d\u4f1a\u4f7f\u7528\u3002\u5982\u679c\u6709 Provider \u4f46 value \u662f undefined\uff0c\u6d88\u8d39\u7ec4\u4ef6\u83b7\u53d6\u7684\u503c\u4e5f\u662f undefined \u800c\u975e\u9ed8\u8ba4\u503c<\/p>\n<\/div><\/div>\n\n\n\n
          4.useRef\u5f15\u7528\u94a9\u5b50<\/h2>\n\n\n\n
          4.1\u4f7f\u7528\u573a\u666f<\/h3>\n\n\n\n
          useRef<\/code> \u6709\u4e24\u4e2a\u4e3b\u8981\u7528\u9014\uff1a<\/p>\n\n\n\n
            \n
          1. \u83b7\u53d6\u7ec4\u4ef6\u5185\u90e8\u7684 DOM \u8282\u70b9\u5f15\u7528<\/li>\n\n\n\n
          2. \u5728\u591a\u6b21\u6e32\u67d3\u4e4b\u95f4\u5b58\u50a8\u4e00\u4e2a\u4e0d\u4f1a\u89e6\u53d1\u91cd\u65b0\u6e32\u67d3\u7684\u503c<\/li>\n<\/ol>\n\n\n\n
            \u9002\u7528\u4e8e\u4ee5\u4e0b\u573a\u666f\uff1a<\/p>\n\n\n\n
              \n
            • \u8bbf\u95ee\u548c\u64cd\u4f5c DOM \u5143\u7d20\uff08\u5982\u805a\u7126\u3001\u6d4b\u91cf\u5c3a\u5bf8\uff09<\/li>\n\n\n\n
            • \u5b58\u50a8\u524d\u4e00\u4e2a\u72b6\u6001\u503c<\/li>\n\n\n\n
            • \u4fdd\u5b58\u5b9a\u65f6\u5668 ID\u3001\u52a8\u753b\u5e27 ID \u7b49<\/li>\n\n\n\n
            • \u5b58\u50a8\u4e0d\u9700\u8981\u89e6\u53d1\u91cd\u65b0\u6e32\u67d3\u7684\u6570\u636e<\/li>\n\n\n\n
            • \u8ba1\u6570\u5668\u6216\u6807\u5fd7\uff08\u5982\u6e32\u67d3\u6b21\u6570\uff09<\/li>\n<\/ul>\n\n\n\n
              4.2\u4f7f\u7528\u793a\u4f8b<\/h3>\n\n\n\n
              import { useRef, useState, useEffect } from 'react'\n\nconst TextInputWithFocusButton = () => {\n  \/\/ \u521b\u5efa\u4e00\u4e2aref\u6765\u5b58\u50a8input\u5143\u7d20\u7684\u5f15\u7528\n  const inputRef = useRef<HTMLInputElement>(null)\n  \n  \/\/ \u521b\u5efa\u4e00\u4e2aref\u6765\u5b58\u50a8\u6e32\u67d3\u6b21\u6570\uff08\u4e0d\u4f1a\u89e6\u53d1\u91cd\u65b0\u6e32\u67d3\uff09\n  const renderCountRef = useRef<number>(0)\n  \n  const [text, setText] = useState<string>('')\n  \n  \/\/ \u70b9\u51fb\u6309\u94ae\u65f6\u805a\u7126\u8f93\u5165\u6846\n  const handleFocus = () => {\n    \/\/ \u4f7f\u7528ref\u8bbf\u95eeDOM\u5143\u7d20\n    if (inputRef.current) {\n      inputRef.current.focus()\n    }\n  }\n  \n  useEffect(() => {\n    \/\/ \u6bcf\u6b21\u6e32\u67d3\u540e\u589e\u52a0\u8ba1\u6570\n    renderCountRef.current += 1\n    console.log(`\u7ec4\u4ef6\u5df2\u6e32\u67d3 ${renderCountRef.current} \u6b21`)\n  })\n  \n  return (\n    <div>\n      <input\n        ref={inputRef}\n        type=\"text\"\n        value={text}\n        onChange={(e) => setText(e.target.value)}\n        placeholder=\"\u8bf7\u8f93\u5165\u6587\u672c\"\n      \/>\n      <button onClick={handleFocus}>\u805a\u7126\u8f93\u5165\u6846<\/button>\n      <p>\u5f53\u524d\u6587\u672c: {text}<\/p>\n      <p>\u6e32\u67d3\u6b21\u6570: {renderCountRef.current}<\/p>\n    <\/div>\n  )\n}<\/code><\/pre>\n\n\n\n
              useRef<\/code> \u63a5\u6536\u4e00\u4e2a\u521d\u59cb\u503c\u53c2\u6570\uff0c\u8fd4\u56de\u4e00\u4e2a\u53ef\u53d8\u7684 ref \u5bf9\u8c61\uff0c\u5176 .current<\/code> \u5c5e\u6027\u88ab\u521d\u59cb\u5316\u4e3a\u4f20\u5165\u7684\u53c2\u6570<\/p>\n\n\n\n
              \u8fd4\u56de\u7684 ref \u5bf9\u8c61\u5728\u7ec4\u4ef6\u7684\u6574\u4e2a\u751f\u547d\u5468\u671f\u5185\u4fdd\u6301\u4e0d\u53d8\uff0c\u5373\u4f7f\u7ec4\u4ef6\u91cd\u65b0\u6e32\u67d3\uff0cref \u5bf9\u8c61\u4e5f\u4e0d\u4f1a\u6539\u53d8<\/strong><\/p>\n\n\n\n
              4.3\u6ce8\u610f\u4e8b\u9879<\/h3>\n\n\n\n
              4.3.1 \u4fee\u6539\u4e0d\u4f1a\u89e6\u53d1\u91cd\u65b0\u6e32\u67d3<\/h4>\n\n\n\n
              \u4fee\u6539 ref.current<\/code> \u503c\u4e0d\u4f1a\u5bfc\u81f4\u7ec4\u4ef6\u91cd\u65b0\u6e32\u67d3\uff0c\u8fd9\u662f\u5b83\u4e0e state \u7684\u4e3b\u8981\u533a\u522b<\/p>\n\n\n\n
              4.3.2 DOM\u5f15\u7528\u65f6\u673a<\/h4>\n\n\n\n
              \u5f53\u7528\u4e8e\u5f15\u7528 DOM \u5143\u7d20\u65f6\uff0cref \u5bf9\u8c61\u7684 .current<\/code> \u5c5e\u6027\u5728\u7ec4\u4ef6\u6302\u8f7d\u65f6\u8bbe\u7f6e\u4e3a\u5bf9\u5e94\u7684 DOM \u5143\u7d20\uff0c\u5728\u5378\u8f7d\u65f6\u8bbe\u7f6e\u4e3a null<\/code><\/p>\n\n\n\n
              4.3.3 \u4e0e\u72b6\u6001\u7684\u533a\u522b<\/h4>\n\n\n\n
              \u4e0e useState<\/code> \u4e0d\u540c\uff0c useRef<\/code> \u662f\u53ef\u53d8\u7684\uff0c\u53ef\u4ee5\u76f4\u63a5\u4fee\u6539 .current<\/code> \u5c5e\u6027\uff0c\u4e14\u4fee\u6539\u4e0d\u4f1a\u89e6\u53d1\u91cd\u65b0\u6e32\u67d3<\/p>\n\n\n\n
              5.useReducer\u503c\u7ba1\u7406\u94a9\u5b50<\/h2>\n\n\n\n
              5.1\u4f7f\u7528\u573a\u666f<\/h3>\n\n\n\n
              \u5f53\u72b6\u6001\u903b\u8f91\u8f83\u590d\u6742\u6216\u72b6\u6001\u4e4b\u95f4\u6709\u4f9d\u8d56\u65f6\uff0c\u53ef\u4ee5\u4f7f\u7528 useReducer<\/code> \u6765\u66ff\u4ee3 useState<\/code> <\/p>\n\n\n\n
              \u9002\u7528\u4e8e\u4ee5\u4e0b\u573a\u666f\uff1a<\/p>\n\n\n\n
                \n
              • \u72b6\u6001\u903b\u8f91\u590d\u6742\uff0c\u5305\u542b\u591a\u4e2a\u5b50\u503c<\/li>\n\n\n\n
              • \u4e0b\u4e00\u4e2a\u72b6\u6001\u4f9d\u8d56\u4e8e\u4e4b\u524d\u7684\u72b6\u6001<\/li>\n\n\n\n
              • \u9700\u8981\u96c6\u4e2d\u7ba1\u7406\u76f8\u5173\u72b6\u6001\u7684\u66f4\u65b0\u903b\u8f91<\/li>\n\n\n\n
              • \u72b6\u6001\u66f4\u65b0\u6d89\u53ca\u6df1\u5c42\u5d4c\u5957\u5bf9\u8c61<\/li>\n\n\n\n
              • \u9700\u8981\u5728\u591a\u4e2a\u7ec4\u4ef6\u95f4\u5171\u4eab\u72b6\u6001\u903b\u8f91<\/li>\n<\/ul>\n\n\n\n
                5.2\u4f7f\u7528\u793a\u4f8b<\/h3>\n\n\n\n
                import { useReducer } from 'react'\n\n\/\/ \u5b9a\u4e49\u72b6\u6001\u7c7b\u578b\u548c\u52a8\u4f5c\u7c7b\u578b\ntype State = { count: number }\ntype Action = \n  | { type: 'increment' }\n  | { type: 'decrement' }\n  | { type: 'reset' }\n\n\/\/ \u5b9a\u4e49reducer\u51fd\u6570\nconst reducer = (state: State, action: Action): State => {\n  switch (action.type) {\n    case 'increment':\n      return { count: state.count + 1 }\n    case 'decrement':\n      return { count: state.count - 1 }\n    case 'reset':\n      return { count: 0 }\n    default:\n      return state\n  }\n}\n\nconst Counter = () => {\n  \/\/ \u4f7f\u7528useReducer\uff0c\u4f20\u5165reducer\u51fd\u6570\u548c\u521d\u59cb\u72b6\u6001\n  const [state, dispatch] = useReducer(reducer, { count: 0 })\n  \n  return (\n    <div>\n      <p>\u8ba1\u6570: {state.count}<\/p>\n      <button onClick={() => dispatch({ type: 'increment' })}>\u589e\u52a0<\/button>\n      <button onClick={() => dispatch({ type: 'decrement' })}>\u51cf\u5c11<\/button>\n      <button onClick={() => dispatch({ type: 'reset' })}>\u91cd\u7f6e<\/button>\n    <\/div>\n  )\n}<\/code><\/pre>\n\n\n\n
                useReducer<\/code> \u63a5\u6536\u4e09\u4e2a\u53c2\u6570\uff1a<\/p>\n\n\n\n
                  \n
                1. reducer<\/code> \u51fd\u6570\uff1a\u63a5\u6536\u5f53\u524d\u72b6\u6001\u548c\u52a8\u4f5c\uff0c\u8fd4\u56de\u65b0\u72b6\u6001<\/li>\n\n\n\n
                2. \u521d\u59cb\u72b6\u6001\uff1a\u53ef\u4ee5\u662f\u503c\u6216\u521d\u59cb\u5316\u51fd\u6570<\/li>\n\n\n\n
                3. \u521d\u59cb\u5316\u51fd\u6570\uff08\u53ef\u9009\uff09\uff1a\u7528\u4e8e\u60f0\u6027\u521d\u59cb\u5316\u72b6\u6001<\/li>\n<\/ol>\n\n\n\n
                  \u8fd4\u56de\u5f53\u524d\u72b6\u6001\u548c dispatch<\/code> \u65b9\u6cd5\u3002\u901a\u8fc7 dispatch<\/code> \u89e6\u53d1\u72b6\u6001\u66f4\u65b0\uff0c\u4f20\u5165\u7684\u52a8\u4f5c\u4f1a\u88ab\u4f20\u9012\u7ed9 reducer \u51fd\u6570<\/p>\n\n\n\n
                  5.3\u6ce8\u610f\u4e8b\u9879<\/h3>\n\n\n\n
                  5.3.1 \u4e0eRedux\u7684\u533a\u522b<\/h4>\n\n\n\n
                  useReducer<\/code> \u662f Redux \u6a21\u5f0f\u7684\u7b80\u5316\u7248\uff0c\u4f46\u4e0d\u5305\u542b\u4e2d\u95f4\u4ef6\u3001\u7ec4\u5408 reducer\u3001\u65f6\u95f4\u65c5\u884c\u8c03\u8bd5\u7b49\u9ad8\u7ea7\u529f\u80fd<\/p>\n\n\n\n
                  5.3.2 \u6027\u80fd\u4f18\u5316<\/h4>\n\n\n\n
                  \u4e0e useState \u4e0d\u540c\uff0c\u5982\u679c dispatch \u7684\u52a8\u4f5c\u6ca1\u6709\u5bfc\u81f4\u72b6\u6001\u53d8\u5316\uff08\u8fd4\u56de\u76f8\u540c\u7684\u72b6\u6001\u5f15\u7528\uff09\uff0cReact \u4e0d\u4f1a\u89e6\u53d1\u91cd\u65b0\u6e32\u67d3<\/p>\n\n\n\n
                  5.3.3 \u72b6\u6001\u5171\u4eab<\/h4>\n\n\n\n
                  \u53ef\u4ee5\u7ed3\u5408 useContext \u5b9e\u73b0\u8de8\u7ec4\u4ef6\u7684\u72b6\u6001\u5171\u4eab\uff0c\u4f5c\u4e3a\u7b80\u6613\u7684\u72b6\u6001\u7ba1\u7406\u89e3\u51b3\u65b9\u6848<\/p>\n\n\n\n
                  6.\u00a0useMemo\u503c\u7f13\u5b58\u94a9\u5b50<\/h2>\n\n\n\n
                  6.1 \u4f7f\u7528\u573a\u666f<\/h3>\n\n\n\n
                  \u5f53\u4e00\u4e2a\u8ba1\u7b97\u8fc7\u7a0b\u5f00\u9500\u8f83\u5927\u65f6\uff0c\u53ef\u4ee5\u901a\u8fc7 useMemo<\/code> \u7f13\u5b58\u8ba1\u7b97\u7ed3\u679c\uff0c\u907f\u514d\u6bcf\u6b21\u6e32\u67d3\u90fd\u91cd\u65b0\u8ba1\u7b97\u3002\u9002\u7528\u4e8e\u4ee5\u4e0b\u573a\u666f\uff1a<\/p>\n\n\n\n
                    \n
                  • \u590d\u6742\u8ba1\u7b97\u6216\u6570\u636e\u5904\u7406\uff08\u5982\u6392\u5e8f\u3001\u8fc7\u6ee4\u5927\u578b\u6570\u7ec4\uff09<\/li>\n\n\n\n
                  • \u6602\u8d35\u7684\u683c\u5f0f\u5316\u64cd\u4f5c<\/li>\n\n\n\n
                  • \u9700\u8981\u4fdd\u6301\u5bf9\u8c61\u5f15\u7528\u7a33\u5b9a\u4ee5\u907f\u514d\u5b50\u7ec4\u4ef6\u91cd\u65b0\u6e32\u67d3<\/li>\n\n\n\n
                  • \u4f5c\u4e3a\u5176\u4ed6 Hook \u7684\u4f9d\u8d56\u9879\u65f6\uff0c\u907f\u514d\u4e0d\u5fc5\u8981\u7684\u91cd\u65b0\u8ba1\u7b97<\/li>\n<\/ul>\n\n\n\n
                    6.2 \u4f7f\u7528\u793a\u4f8b<\/h3>\n\n\n\n
                    \u7f13\u5b58\u8ba1\u7b97\u7ed3\u679c<\/p>\n\n\n\n
                    import { useState, useMemo } from 'react'\n\nconst ExpensiveCalculation = () => {\n  const [count, setCount] = useState<number>(0)\n  const [wordIndex, setWordIndex] = useState<number>(0)\n  \n  const words = ['React', 'JavaScript', 'TypeScript', 'Hooks', 'Components']\n  \n  \/\/ \u6a21\u62df\u6602\u8d35\u7684\u8ba1\u7b97\u8fc7\u7a0b<\/em>\n  const expensiveComputation = (num: number) => {\n    console.log('\u6267\u884c\u6602\u8d35\u8ba1\u7b97...')\n    \/\/ \u6a21\u62df\u8017\u65f6\u64cd\u4f5c<\/em>\n    let result = 0\n    for (let i = 0; i < 1000000; i++) {\n      result += num\n    }\n    return result\n  }\n  \n  \/\/ \u4f7f\u7528useMemo\u7f13\u5b58\u8ba1\u7b97\u7ed3\u679c\uff0c\u53ea\u6709\u5f53count\u53d8\u5316\u65f6\u624d\u91cd\u65b0\u8ba1\u7b97<\/em>\n  const computedValue = useMemo(() => {\n    return expensiveComputation(count)\n  }, [count])\n  \n  return (\n    <div>\n      <p>\u5f53\u524d\u8ba1\u6570: {count}<\/p>\n      <p>\u8ba1\u7b97\u7ed3\u679c: {computedValue}<\/p>\n      <p>\u5f53\u524d\u5355\u8bcd: {words[wordIndex]}<\/p>\n      \n      <button onClick={() => setCount(count + 1)}>\u589e\u52a0\u8ba1\u6570<\/button>\n      <button onClick={() => setWordIndex((wordIndex + 1) % words.length)}>\n        \u5207\u6362\u5355\u8bcd (\u4e0d\u4f1a\u89e6\u53d1\u91cd\u65b0\u8ba1\u7b97)\n      <\/button>\n    <\/div>\n  )\n}<\/code><\/pre>\n\n\n\n
                    useMemo<\/code> \u63a5\u6536\u4e24\u4e2a\u53c2\u6570\uff1a<\/p>\n\n\n\n
                      \n
                    1. \u521b\u5efa\u503c\u7684\u5de5\u5382\u51fd\u6570<\/li>\n\n\n\n
                    2. \u4f9d\u8d56\u6570\u7ec4\uff1a\u53ea\u6709\u5f53\u4f9d\u8d56\u9879\u53d8\u5316\u65f6\uff0c\u624d\u4f1a\u91cd\u65b0\u8ba1\u7b97\u503c<\/li>\n<\/ol>\n\n\n\n
                      \u8fd4\u56de\u503c\u662f\u7f13\u5b58\u7684\u8ba1\u7b97\u7ed3\u679c\uff0c\u5728\u4f9d\u8d56\u4e0d\u53d8\u7684\u60c5\u51b5\u4e0b\uff0c\u591a\u6b21\u6e32\u67d3\u65f6\u8fd4\u56de\u76f8\u540c\u7684\u503c\u5f15\u7528<\/p>\n\n\n\n
                      6.3 \u6ce8\u610f\u4e8b\u9879<\/h3>\n\n\n\n
                      6.3.1 \u4e0d\u8981\u8fc7\u5ea6\u4f7f\u7528<\/h4>\n\n\n\n
                      \u53ea\u6709\u5f53\u8ba1\u7b97\u771f\u6b63\u6602\u8d35\u6216\u9700\u8981\u4fdd\u6301\u5f15\u7528\u7a33\u5b9a\u65f6\u624d\u4f7f\u7528 useMemo<\/code> \uff0c\u5426\u5219\u53ef\u80fd\u56e0\u4e3a\u989d\u5916\u7684\u8bb0\u5fc6\u5316\u5f00\u9500\u800c\u9002\u5f97\u5176\u53cd<\/p>\n\n\n\n
                      6.3.2 \u4f9d\u8d56\u9879\u7ba1\u7406<\/h4>\n\n\n\n
                      \u4f9d\u8d56\u6570\u7ec4\u5e94\u5305\u542b\u5de5\u5382\u51fd\u6570\u4e2d\u4f7f\u7528\u7684\u6240\u6709\u7ec4\u4ef6\u5185\u7684\u53d8\u91cf\u548c\u72b6\u6001\uff0c\u786e\u4fdd\u5728\u76f8\u5173\u6570\u636e\u53d8\u5316\u65f6\u91cd\u65b0\u8ba1\u7b97<\/p>\n\n\n\n
                      6.3.3 \u4e0eReact.memo\u7684\u533a\u522b<\/h4>\n\n\n\n
                      useMemo<\/code>\u00a0\u7f13\u5b58\u7ec4\u4ef6\u5185\u7684\u8ba1\u7b97\u7ed3\u679c\uff0c\u800c\u00a0React.memo<\/code>\u00a0\u7f13\u5b58\u6574\u4e2a\u7ec4\u4ef6\u7684\u6e32\u67d3\u7ed3\u679c<\/p>\n\n\n\n
                      <\/p>\n","protected":false},"excerpt":{"rendered":"
                      \u53ca\u65f6\u66f4\u65b0\u4e2d…… 1.useState\u72b6\u6001\u94a9\u5b50 1.1\u4f7f\u7528\u573a\u666f \u5f53\u4e00\u4e2a\u6570\u636e\u9700\u8981\u54cd\u5e94\u5f0f\u5448\u73b0 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[47,1],"tags":[],"class_list":["post-1875","post","type-post","status-publish","format-standard","hentry","category-react","category-1"],"_links":{"self":[{"href":"https:\/\/womeifei.cn\/index.php\/wp-json\/wp\/v2\/posts\/1875","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/womeifei.cn\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/womeifei.cn\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/womeifei.cn\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/womeifei.cn\/index.php\/wp-json\/wp\/v2\/comments?post=1875"}],"version-history":[{"count":10,"href":"https:\/\/womeifei.cn\/index.php\/wp-json\/wp\/v2\/posts\/1875\/revisions"}],"predecessor-version":[{"id":1916,"href":"https:\/\/womeifei.cn\/index.php\/wp-json\/wp\/v2\/posts\/1875\/revisions\/1916"}],"wp:attachment":[{"href":"https:\/\/womeifei.cn\/index.php\/wp-json\/wp\/v2\/media?parent=1875"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/womeifei.cn\/index.php\/wp-json\/wp\/v2\/categories?post=1875"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/womeifei.cn\/index.php\/wp-json\/wp\/v2\/tags?post=1875"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}