{"id":38640,"date":"2023-03-29T16:59:54","date_gmt":"2024-01-22T10:31:04","guid":{"rendered":"https:\/\/www.silicloud.com\/zh\/blog\/%e7%90%86%e8%a7%a3%e5%92%8c%e4%bd%bf%e7%94%a8-react-memo-usecallback-usememo-%e5%8f%af%e4%bb%a5%e8%bf%9b%e8%a1%8c%e6%80%a7%e8%83%bd%e4%bc%98%e5%8c%96%e3%80%82\/"},"modified":"2024-04-29T21:02:40","modified_gmt":"2024-04-29T13:02:40","slug":"%e7%90%86%e8%a7%a3%e5%92%8c%e4%bd%bf%e7%94%a8-react-memo-usecallback-usememo-%e5%8f%af%e4%bb%a5%e8%bf%9b%e8%a1%8c%e6%80%a7%e8%83%bd%e4%bc%98%e5%8c%96%e3%80%82","status":"publish","type":"post","link":"https:\/\/www.silicloud.com\/zh\/blog\/%e7%90%86%e8%a7%a3%e5%92%8c%e4%bd%bf%e7%94%a8-react-memo-usecallback-usememo-%e5%8f%af%e4%bb%a5%e8%bf%9b%e8%a1%8c%e6%80%a7%e8%83%bd%e4%bc%98%e5%8c%96%e3%80%82\/","title":{"rendered":"\u7406\u89e3\u548c\u4f7f\u7528 React.memo \/ useCallback \/ useMemo \u53ef\u4ee5\u8fdb\u884c\u6027\u80fd\u4f18\u5316"},"content":{"rendered":"<h2>\u9996\u5148<\/h2>\n<p>\u4ee5\u4e0b\u662f\u5173\u4e8eReact\uff08v16.12.0\uff09\u7684React.memo\u3001useCallback\u548cuseMemo\u7684\u57fa\u672c\u7528\u6cd5\u548c\u9002\u7528\u573a\u666f\u7684\u5907\u5fd8\u5f55\u3002<\/p>\n<ul class=\"post-ul\">\n<li style=\"list-style-type: none;\">\n<ul class=\"post-ul\">\u300cReact \u3067\u306e\u30d1\u30d5\u30a9\u30fc\u30de\u30f3\u30b9\u6700\u9069\u5316\u306e\u624b\u6bb5\u3092\u77e5\u308a\u305f\u3044\u300d<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<ul class=\"post-ul\">\u300c\u306a\u305cReact.memo\u3001useCallback\u3001useMemo\u3092\u5229\u7528\u3059\u308b\u306e\u304b\u308f\u304b\u3089\u306a\u3044\u300d<\/ul>\n<p>\u9019\u662f\u70ba\u4e86\u9019\u6a23\u7684\u4eba\u6240\u5beb\u7684\u6587\u7ae0\u3002<\/p>\n<p>\u8fd9\u4e2a\u793a\u8303\u653e\u5728 CodeSandbox \u4e0a\u3002\u7f16\u8f91\u5e76\u786e\u8ba4\u8fd0\u4f5c\u60c5\u51b5\u540e\uff0c\u6211\u8ba4\u4e3a\u4f60\u4f1a\u66f4\u6df1\u523b\u5730\u7406\u89e3\u3002<\/p>\n<h3>\u8be5\u6587\u7ae0\u6240\u4f7f\u7528\u7684\u672f\u8bed<\/h3>\n<ul class=\"post-ul\">\n<li style=\"list-style-type: none;\">\n<ul class=\"post-ul\">\u30e1\u30e2\u5316<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<ul class=\"post-ul\">\u8a08\u7b97\u7d50\u679c<\/ul>\n<h4>\u8bb0\u5fc6\u5316<\/h4>\n<p>\u4fdd\u7559\u8ba1\u7b97\u7ed3\u679c\u5e76\u518d\u6b21\u5229\u7528\u7684\u65b9\u6cd5\u3002<\/p>\n<p>\u6211\u8ba4\u4e3a\u53ef\u4ee5\u5c06\u5176\u60f3\u8c61\u4e3a\u7c7b\u4f3c\u4e8e\u7f13\u5b58\u7684\u4e1c\u897f\u3002<\/p>\n<p>\u56e0\u6b64\uff0c\u4ee5\u4e0b\u8fd9\u4e9b\u8bcd\u8bed\u7684\u610f\u601d\u5927\u81f4\u76f8\u540c\u3002<\/p>\n<ul class=\"post-ul\">\n<li style=\"list-style-type: none;\">\n<ul class=\"post-ul\">\u300c\u30e1\u30e2\u5316\u3055\u308c\u305f\u5024\u300d=\u300c\u8a08\u7b97\u7d50\u679c\u304c\u4fdd\u6301\u3055\u308c\u305f\u5024\u300d<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<ul class=\"post-ul\">\u300c\u30e1\u30e2\u5316\u3059\u308b\u300d=\u300c\u8a08\u7b97\u7d50\u679c\u3092\u518d\u5229\u7528\u3067\u304d\u308b\u3088\u3046\u306b\u4fdd\u6301\u3059\u308b\u300d<\/ul>\n<p>\u7531\u4e8e\u4f7f\u7528\u4e86\u8bb0\u5fc6\u5316\u6280\u672f\uff0c\u4e0d\u518d\u9700\u8981\u6bcf\u6b21\u8fdb\u884c\u8ba1\u7b97\uff0c\u56e0\u6b64\u53ef\u4ee5\u671f\u671b\u6027\u80fd\u7684\u63d0\u5347\u3002<\/p>\n<h4>\u8a08\u7b97\u7684\u7d50\u679c<\/h4>\n<p>\u4ee5\u4e0b\u662f\u8ba1\u7b97\u7684\u7ed3\u679c\u4e4b\u7c7b\u7684\u3002<\/p>\n<pre class=\"post-pre\"><code><span class=\"c1\">\/\/ result \u306f 1 + 2 \u306e\u8a08\u7b97\u7d50\u679c\u3092\u683c\u7d0d\u3057\u3066\u3044\u308b\u5909\u6570<\/span>\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">result<\/span> <span class=\"o\">=<\/span> <span class=\"mi\">1<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">2<\/span><span class=\"p\">;<\/span>\r\n\r\n<span class=\"c1\">\/\/ result2 \u306f [1, 2, 3, 4, 5].map(number =&gt; number * 2) \u306e\u8a08\u7b97\u7d50\u679c\u3092\u683c\u7d0d\u3057\u3066\u3044\u308b\u5909\u6570<\/span>\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">result2<\/span> <span class=\"o\">=<\/span> <span class=\"p\">[<\/span><span class=\"mi\">1<\/span><span class=\"p\">,<\/span> <span class=\"mi\">2<\/span><span class=\"p\">,<\/span> <span class=\"mi\">3<\/span><span class=\"p\">,<\/span> <span class=\"mi\">4<\/span><span class=\"p\">,<\/span> <span class=\"mi\">5<\/span><span class=\"p\">].<\/span><span class=\"nf\">map<\/span><span class=\"p\">(<\/span><span class=\"nx\">number<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nx\">number<\/span> <span class=\"o\">*<\/span> <span class=\"mi\">2<\/span><span class=\"p\">);<\/span>\r\n\r\n<span class=\"c1\">\/\/ result3 \u306f React.createElement(\"div\", null, `Hello ${this.props.name}`) \u306e\u8a08\u7b97\u7d50\u679c\u3092\u683c\u7d0d\u3057\u3066\u3044\u308b\u5909\u6570<\/span>\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">result3<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">React<\/span><span class=\"p\">.<\/span><span class=\"nf\">createElement<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">div<\/span><span class=\"dl\">\"<\/span><span class=\"p\">,<\/span> <span class=\"kc\">null<\/span><span class=\"p\">,<\/span> <span class=\"s2\">`Hello <\/span><span class=\"p\">${<\/span><span class=\"k\">this<\/span><span class=\"p\">.<\/span><span class=\"nx\">props<\/span><span class=\"p\">.<\/span><span class=\"nx\">name<\/span><span class=\"p\">}<\/span><span class=\"s2\">`<\/span><span class=\"p\">);<\/span>\r\n<\/code><\/pre>\n<h2>\u5728 React \u4e2d\u8fdb\u884c\u6027\u80fd\u4f18\u5316\u3002<\/h2>\n<p>\u5728React\u4e2d\uff0c\u6291\u5236\u4e0d\u5fc5\u8981\u7684\u91cd\u65b0\u8ba1\u7b97\u548c\u7ec4\u4ef6\u91cd\u65b0\u6e32\u67d3\u662f\u57fa\u672c\u7684\u6027\u80fd\u4f18\u5316\u7b56\u7565\u3002<\/p>\n<p>\u4f7f\u7528React.memo\u3001useCallback\u548cuseMemo\u4f5c\u4e3a\u5b9e\u73b0\u8fd9\u4e9b\u7684\u624b\u6bb5\u3002<\/p>\n<p>\u65e0\u8bba\u662f\u5728React\u4e4b\u5916\u7684\u6027\u80fd\u8c03\u4f18\uff0c\u8fd8\u662f\u5728\u5176\u4ed6\u65b9\u9762\uff0c\u6d4b\u91cf\u90fd\u662f\u5fc5\u4e0d\u53ef\u5c11\u7684\u3002<\/p>\n<p>\u5728\u6ca1\u6709\u610f\u4e49\u7684\u60c5\u51b5\u4e0b\uff0c\u968f\u610f\u4f7f\u7528\u5e76\u4e0d\u80fd\u63d0\u9ad8\u6027\u80fd\uff0c\u6709\u65f6\u751a\u81f3\u6ca1\u6709\u610f\u4e49\uff0c\u6240\u4ee5\u8bf7\u6ce8\u610f\u3002<\/p>\n<h2>React.memo\u662fReact\u4e2d\u7684\u4e00\u4e2a\u9ad8\u9636\u7ec4\u4ef6\u3002<\/h2>\n<p>React \u7684 API\uff08\u65b9\u6cd5\uff09\uff0c\u7528\u4e8e\u5bf9\u7ec4\u4ef6\uff08\u7ec4\u4ef6\u6e32\u67d3\u7ed3\u679c\uff09\u8fdb\u884c\u8bb0\u5fc6\u5316\u3002<\/p>\n<p>\u901a\u8fc7\u5bf9\u7ec4\u4ef6\u8fdb\u884c\u8bb0\u5fc6\u5316\u5904\u7406\uff0c\u53ef\u4ee5\u8df3\u8fc7\u7ec4\u4ef6\u7684\u91cd\u65b0\u6e32\u67d3\u3002<\/p>\n<h3>\u4e3a\u4ec0\u4e48\u8981\u4f7f\u7528 React.memo?<\/h3>\n<p>\u901a\u8fc7\u8df3\u8fc7\u91cd\u65b0\u6e32\u67d3\u7c7b\u4f3c\u7684\u7ec4\u4ef6\uff0c\u53ef\u4ee5\u671f\u5f85\u63d0\u9ad8\u6027\u80fd\u3002<\/p>\n<ul class=\"post-ul\">\n<li style=\"list-style-type: none;\">\n<ul class=\"post-ul\">\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u30b3\u30b9\u30c8\u304c\u9ad8\u3044\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8<\/ul>\n<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<ul class=\"post-ul\">\u983b\u7e41\u306b\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u308b\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u5185\u306e\u5b50\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8<\/ul>\n<p>\u5bf9\u4e8e\u5e38\u89c4\u7ec4\u4ef6\uff0c\u6ca1\u5fc5\u8981\u8d39\u5fc3\u4f7f\u7528React.memo\u3002<\/p>\n<h3>React.memo \u7684\u8bed\u6cd5<\/h3>\n<pre class=\"post-pre\"><code><span class=\"nx\">React<\/span><span class=\"p\">.<\/span><span class=\"nf\">memo<\/span><span class=\"p\">(<\/span><span class=\"nx\">\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8<\/span><span class=\"p\">);<\/span>\r\n<\/code><\/pre>\n<p>\u6bd4\u5982\uff0c\u5982\u679c\u8981\u5bf9\u540d\u4e3aHello\u7684\u7ec4\u4ef6\u8fdb\u884c\u8bb0\u5fc6\u5316\uff0c\u53ef\u4ee5\u6309\u7167\u5982\u4e0b\u65b9\u5f0f\u8fdb\u884c\u3002<\/p>\n<pre class=\"post-pre\"><code><span class=\"kd\">const<\/span> <span class=\"nx\">Hello<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">React<\/span><span class=\"p\">.<\/span><span class=\"nf\">memo<\/span><span class=\"p\">(<\/span><span class=\"nx\">props<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"k\">return<\/span> <span class=\"p\">&lt;<\/span><span class=\"nt\">h1<\/span><span class=\"p\">&gt;<\/span>Hello <span class=\"si\">{<\/span><span class=\"nx\">props<\/span><span class=\"p\">.<\/span><span class=\"nx\">name<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">h1<\/span><span class=\"p\">&gt;;<\/span>\r\n<span class=\"p\">});<\/span>\r\n<\/code><\/pre>\n<p>React.memo\u4f1a\u68c0\u67e5Props\u7684\u7b49\u4ef7\u6027\uff08\u5373\u503c\u662f\u5426\u76f8\u7b49\uff09\u6765\u5224\u65ad\u662f\u5426\u91cd\u65b0\u6e32\u67d3\u3002<\/p>\n<p>\u5bf9\u6bd4\u65b0\u4f20\u9012\u7684 Props \u548c\u4e0a\u6b21\u7684 Props \uff0c\u82e5\u5b83\u4eec\u76f8\u7b49\uff0c\u5219\u91cd\u7528\u5df2\u7ecf\u8fdb\u884c\u4e86\u8bb0\u5fc6\u5316\u7684\u7ec4\u4ef6\uff0c\u800c\u4e0d\u8fdb\u884c\u91cd\u65b0\u6e32\u67d3\u3002<\/p>\n<p>\u56e0\u6b64\uff0c\u5728\u4e0a\u8ff0\u7684Hello\u7ec4\u4ef6\u4e2d\uff0c\u53ea\u8981props.name\u4e0d\u88ab\u66f4\u65b0\uff0c\u8be5\u7ec4\u4ef6\u5c31\u4e0d\u4f1a\u91cd\u65b0\u6e32\u67d3\u3002<\/p>\n<h3>React.memo \u7684\u4f7f\u7528\u793a\u4f8b<\/h3>\n<p>\u5c1d\u8bd5\u6bd4\u8f83\u4e00\u4e0b\u4f7f\u7528 React.memo \u548c\u4e0d\u4f7f\u7528 React.memo \u6709\u54ea\u4e9b\u533a\u522b\u3002<\/p>\n<h4>\u5982\u679c\u4e0d\u4f7f\u7528React.memo<\/h4>\n<p>\u4e00\u822c\u6765\u8bf4\uff0c\u5f53\u7ec4\u4ef6\u7684\u72b6\u6001\u66f4\u65b0\u65f6\uff0c\u8be5\u7ec4\u4ef6\u5c06\u91cd\u65b0\u6e32\u67d3\u3002<\/p>\n<div><img decoding=\"async\" class=\"post-images\" title=\"\" src=\"https:\/\/cdn.silicloud.com\/blog-img\/blog\/img\/657d356037434c4406c6c4a2\/39-0.gif\" alt=\"react-memo.gif\" \/><\/div>\n<pre class=\"post-pre\"><code><span class=\"k\">import<\/span> <span class=\"nx\">React<\/span><span class=\"p\">,<\/span> <span class=\"p\">{<\/span> <span class=\"nx\">useState<\/span> <span class=\"p\">}<\/span> <span class=\"k\">from<\/span> <span class=\"dl\">\"<\/span><span class=\"s2\">react<\/span><span class=\"dl\">\"<\/span><span class=\"p\">;<\/span>\r\n\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">Child<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">props<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render Child<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"k\">return<\/span> <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>Child: <span class=\"si\">{<\/span><span class=\"nx\">props<\/span><span class=\"p\">.<\/span><span class=\"nx\">count<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;;<\/span>\r\n<span class=\"p\">};<\/span>\r\n\r\n<span class=\"k\">export<\/span> <span class=\"k\">default<\/span> <span class=\"kd\">function<\/span> <span class=\"nf\">App<\/span><span class=\"p\">()<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render App<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count1<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount1<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count2<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount2<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n    <span class=\"p\">&lt;&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount1<\/span><span class=\"p\">(<\/span><span class=\"nx\">count1<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>countup App count<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount2<\/span><span class=\"p\">(<\/span><span class=\"nx\">count2<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>countup Child count<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>App: <span class=\"si\">{<\/span><span class=\"nx\">count1<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nc\">Child<\/span> <span class=\"na\">count<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"nx\">count2<\/span><span class=\"si\">}<\/span> <span class=\"p\">\/&gt;<\/span>\r\n    <span class=\"p\">&lt;\/&gt;<\/span>\r\n  <span class=\"p\">);<\/span>\r\n<span class=\"p\">}<\/span>\r\n<\/code><\/pre>\n<p>\u8fd9\u662f\u6b63\u5e38\u7684\u884c\u4e3a\uff0c\u8fd9\u6837\u5199\u6ca1\u6709\u95ee\u9898\u4e5f\u6ca1\u6709\u9519\u8bef\u3002<\/p>\n<p>\u5982\u679c\u9047\u5230\u7ec4\u4ef6\u4e0d\u5fc5\u8981\u7684\u91cd\u65b0\u6e32\u67d3\u5bfc\u81f4\u6027\u80fd\u95ee\u9898\u7684\u60c5\u51b5\uff0c\u53ef\u4ee5\u8003\u8651\u4f7f\u7528React.memo\u6765\u89e3\u51b3\u3002<\/p>\n<p>\u7531\u4e8e\u672c\u6b21\u60c5\u51b5\u4e0b\uff0c\u5373\u4f7fChild\u7ec4\u4ef6\u603b\u662f\u91cd\u65b0\u6e32\u67d3\u4e5f\u6ca1\u6709\u95ee\u9898\uff0c\u56e0\u6b64\u65e0\u9700\u4f7f\u7528React.memo\u3002<\/p>\n<h4>\u5982\u679c\u60a8\u4f7f\u7528React.memo<\/h4>\n<div><img decoding=\"async\" class=\"post-images\" title=\"\" src=\"https:\/\/cdn.silicloud.com\/blog-img\/blog\/img\/657d356037434c4406c6c4a2\/45-0.gif\" alt=\"using-react-memo.gif\" \/><\/div>\n<pre class=\"post-pre\"><code><span class=\"k\">import<\/span> <span class=\"nx\">React<\/span><span class=\"p\">,<\/span> <span class=\"p\">{<\/span> <span class=\"nx\">useState<\/span> <span class=\"p\">}<\/span> <span class=\"k\">from<\/span> <span class=\"dl\">\"<\/span><span class=\"s2\">react<\/span><span class=\"dl\">\"<\/span><span class=\"p\">;<\/span>\r\n\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">Child<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">React<\/span><span class=\"p\">.<\/span><span class=\"nf\">memo<\/span><span class=\"p\">(<\/span><span class=\"nx\">props<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render Child<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"k\">return<\/span> <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>Child: <span class=\"si\">{<\/span><span class=\"nx\">props<\/span><span class=\"p\">.<\/span><span class=\"nx\">count<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;;<\/span>\r\n<span class=\"p\">});<\/span>\r\n\r\n<span class=\"k\">export<\/span> <span class=\"k\">default<\/span> <span class=\"kd\">function<\/span> <span class=\"nf\">App<\/span><span class=\"p\">()<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render App<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count1<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount1<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count2<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount2<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n    <span class=\"p\">&lt;&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount1<\/span><span class=\"p\">(<\/span><span class=\"nx\">count1<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>countup App count<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount2<\/span><span class=\"p\">(<\/span><span class=\"nx\">count2<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>countup Child count<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>App: <span class=\"si\">{<\/span><span class=\"nx\">count1<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nc\">Child<\/span> <span class=\"na\">count<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"nx\">count2<\/span><span class=\"si\">}<\/span> <span class=\"p\">\/&gt;<\/span>\r\n    <span class=\"p\">&lt;\/&gt;<\/span>\r\n  <span class=\"p\">);<\/span>\r\n<span class=\"p\">}<\/span>\r\n<\/code><\/pre>\n<p>\u5f53\u66f4\u65b0\u8ba1\u65701\u5e76\u91cd\u65b0\u6e32\u67d3App\u7ec4\u4ef6\u65f6\uff0c\u4f20\u9012\u7ed9\u5b50\u7ec4\u4ef6Child\u7684\u5c5e\u6027count2\u4e0d\u4f1a\u66f4\u65b0\uff0c\u56e0\u6b64\u8df3\u8fc7\u4e86\u91cd\u65b0\u6e32\u67d3\u8fc7\u7a0b\u3002<\/p>\n<p>\u53ea\u6709\u5f53\u4f20\u9012\u7ed9\u5b50\u7ec4\u4ef6\u7684count2\u66f4\u65b0\u65f6\uff0c\u624d\u4f1a\u91cd\u65b0\u6e32\u67d3\u3002<\/p>\n<h4>\u7f13\u5b58\u9ad8\u6210\u672c\u7684\u6e32\u67d3\u7ec4\u4ef6\u3002<\/h4>\n<div><img decoding=\"async\" class=\"post-images\" title=\"\" src=\"https:\/\/cdn.silicloud.com\/blog-img\/blog\/img\/657d356037434c4406c6c4a2\/50-0.gif\" alt=\"using-react-memo-02.gif\" \/><\/div>\n<pre class=\"post-pre\"><code><span class=\"k\">import<\/span> <span class=\"nx\">React<\/span><span class=\"p\">,<\/span> <span class=\"p\">{<\/span> <span class=\"nx\">useState<\/span> <span class=\"p\">}<\/span> <span class=\"k\">from<\/span> <span class=\"dl\">\"<\/span><span class=\"s2\">react<\/span><span class=\"dl\">\"<\/span><span class=\"p\">;<\/span>\r\n\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">Child<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">React<\/span><span class=\"p\">.<\/span><span class=\"nf\">memo<\/span><span class=\"p\">(<\/span><span class=\"nx\">props<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"kd\">let<\/span> <span class=\"nx\">i<\/span> <span class=\"o\">=<\/span> <span class=\"mi\">0<\/span><span class=\"p\">;<\/span>\r\n  <span class=\"k\">while <\/span><span class=\"p\">(<\/span><span class=\"nx\">i<\/span> <span class=\"o\">&lt;<\/span> <span class=\"mi\">1000000000<\/span><span class=\"p\">)<\/span> <span class=\"nx\">i<\/span><span class=\"o\">++<\/span><span class=\"p\">;<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render Child<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"k\">return<\/span> <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>Child: <span class=\"si\">{<\/span><span class=\"nx\">props<\/span><span class=\"p\">.<\/span><span class=\"nx\">count<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;;<\/span>\r\n<span class=\"p\">});<\/span>\r\n\r\n<span class=\"k\">export<\/span> <span class=\"k\">default<\/span> <span class=\"kd\">function<\/span> <span class=\"nf\">App<\/span><span class=\"p\">()<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render App<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count1<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount1<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count2<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount2<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n    <span class=\"p\">&lt;&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount1<\/span><span class=\"p\">(<\/span><span class=\"nx\">count1<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>countup App count<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount2<\/span><span class=\"p\">(<\/span><span class=\"nx\">count2<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>countup Child count<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>App: <span class=\"si\">{<\/span><span class=\"nx\">count1<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nc\">Child<\/span> <span class=\"na\">count<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"nx\">count2<\/span><span class=\"si\">}<\/span> <span class=\"p\">\/&gt;<\/span>\r\n    <span class=\"p\">&lt;\/&gt;<\/span>\r\n  <span class=\"p\">);<\/span>\r\n<span class=\"p\">}<\/span>\r\n<\/code><\/pre>\n<h4>\u5bf9\u4e8e\u9891\u7e41\u91cd\u65b0\u6e32\u67d3\u7684\u7ec4\u4ef6\u5185\u7684\u5b50\u7ec4\u4ef6\u8fdb\u884c\u8bb0\u5fc6\u5316\u5904\u7406\u3002<\/h4>\n<div><img decoding=\"async\" class=\"post-images\" title=\"\" src=\"https:\/\/cdn.silicloud.com\/blog-img\/blog\/img\/657d356037434c4406c6c4a2\/53-0.gif\" alt=\"using-react-memo-03.gif\" \/><\/div>\n<pre class=\"post-pre\"><code><span class=\"k\">import<\/span> <span class=\"nx\">React<\/span><span class=\"p\">,<\/span> <span class=\"p\">{<\/span> <span class=\"nx\">useState<\/span><span class=\"p\">,<\/span> <span class=\"nx\">useEffect<\/span><span class=\"p\">,<\/span> <span class=\"nx\">useRef<\/span> <span class=\"p\">}<\/span> <span class=\"k\">from<\/span> <span class=\"dl\">\"<\/span><span class=\"s2\">react<\/span><span class=\"dl\">\"<\/span><span class=\"p\">;<\/span>\r\n\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">Child<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">React<\/span><span class=\"p\">.<\/span><span class=\"nf\">memo<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render Child<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"k\">return<\/span> <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>Child<span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;;<\/span>\r\n<span class=\"p\">});<\/span>\r\n\r\n<span class=\"k\">export<\/span> <span class=\"k\">default<\/span> <span class=\"kd\">function<\/span> <span class=\"nf\">App<\/span><span class=\"p\">()<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render App<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">timeLeft<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setTimeLeft<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">100<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">timerRef<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useRef<\/span><span class=\"p\">(<\/span><span class=\"kc\">null<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">timeLeftRef<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useRef<\/span><span class=\"p\">(<\/span><span class=\"nx\">timeLeft<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"nf\">useEffect<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"nx\">timeLeftRef<\/span><span class=\"p\">.<\/span><span class=\"nx\">current<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">timeLeft<\/span><span class=\"p\">;<\/span>\r\n  <span class=\"p\">},<\/span> <span class=\"p\">[<\/span><span class=\"nx\">timeLeft<\/span><span class=\"p\">]);<\/span>\r\n\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">tick<\/span> <span class=\"o\">=<\/span> <span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"k\">if <\/span><span class=\"p\">(<\/span><span class=\"nx\">timeLeftRef<\/span><span class=\"p\">.<\/span><span class=\"nx\">current<\/span> <span class=\"o\">===<\/span> <span class=\"mi\">0<\/span><span class=\"p\">)<\/span> <span class=\"p\">{<\/span>\r\n      <span class=\"nf\">clearInterval<\/span><span class=\"p\">(<\/span><span class=\"nx\">timerRef<\/span><span class=\"p\">.<\/span><span class=\"nx\">current<\/span><span class=\"p\">);<\/span>\r\n      <span class=\"k\">return<\/span><span class=\"p\">;<\/span>\r\n    <span class=\"p\">}<\/span>\r\n    <span class=\"nf\">setTimeLeft<\/span><span class=\"p\">(<\/span><span class=\"nx\">prevTime<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nx\">prevTime<\/span> <span class=\"o\">-<\/span> <span class=\"mi\">1<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"p\">};<\/span>\r\n\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">start<\/span> <span class=\"o\">=<\/span> <span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"nx\">timerRef<\/span><span class=\"p\">.<\/span><span class=\"nx\">current<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">setInterval<\/span><span class=\"p\">(<\/span><span class=\"nx\">tick<\/span><span class=\"p\">,<\/span> <span class=\"mi\">10<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"p\">};<\/span>\r\n\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">reset<\/span> <span class=\"o\">=<\/span> <span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"nf\">clearInterval<\/span><span class=\"p\">(<\/span><span class=\"nx\">timerRef<\/span><span class=\"p\">.<\/span><span class=\"nx\">current<\/span><span class=\"p\">);<\/span>\r\n    <span class=\"nf\">setTimeLeft<\/span><span class=\"p\">(<\/span><span class=\"mi\">100<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"p\">};<\/span>\r\n\r\n  <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n    <span class=\"p\">&lt;&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"nx\">start<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>start<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"nx\">reset<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>reset<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>App: <span class=\"si\">{<\/span><span class=\"nx\">timeLeft<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nc\">Child<\/span> <span class=\"p\">\/&gt;<\/span>\r\n    <span class=\"p\">&lt;\/&gt;<\/span>\r\n  <span class=\"p\">);<\/span>\r\n<span class=\"p\">}<\/span>\r\n<\/code><\/pre>\n<h3>\u63a5\u6536 Props \u4f5c\u4e3a\u56de\u8c03\u51fd\u6570\u7684\u7ec4\u4ef6\u5fc5\u5b9a\u4f1a\u89e6\u53d1\u91cd\u65b0\u6e32\u67d3\u3002<\/h3>\n<div><img decoding=\"async\" class=\"post-images\" title=\"\" src=\"https:\/\/cdn.silicloud.com\/blog-img\/blog\/img\/657d356037434c4406c6c4a2\/56-0.gif\" alt=\"using-react-memo-04.gif\" \/><\/div>\n<pre class=\"post-pre\"><code><span class=\"k\">import<\/span> <span class=\"nx\">React<\/span><span class=\"p\">,<\/span> <span class=\"p\">{<\/span> <span class=\"nx\">useState<\/span> <span class=\"p\">}<\/span> <span class=\"k\">from<\/span> <span class=\"dl\">\"<\/span><span class=\"s2\">react<\/span><span class=\"dl\">\"<\/span><span class=\"p\">;<\/span>\r\n\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">Child<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">React<\/span><span class=\"p\">.<\/span><span class=\"nf\">memo<\/span><span class=\"p\">(<\/span><span class=\"nx\">props<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render Child<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"k\">return<\/span> <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"nx\">props<\/span><span class=\"p\">.<\/span><span class=\"nx\">handleClick<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Child<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;;<\/span>\r\n<span class=\"p\">});<\/span>\r\n\r\n<span class=\"k\">export<\/span> <span class=\"k\">default<\/span> <span class=\"kd\">function<\/span> <span class=\"nf\">App<\/span><span class=\"p\">()<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render App<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"c1\">\/\/ \u95a2\u6570\u306f\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304c\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u308b\u5ea6\u306b\u518d\u751f\u6210\u3055\u308c\u308b\u305f\u3081\u3001<\/span>\r\n  <span class=\"c1\">\/\/ \u95a2\u6570\u306e\u5185\u5bb9\u304c\u540c\u3058\u3067\u3082\u3001\u65b0\u3057\u3044 handleClick \u3068\u524d\u56de\u306e handleClick \u306f<\/span>\r\n  <span class=\"c1\">\/\/ \u7570\u306a\u308b\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u306a\u306e\u3067\u3001\u7b49\u4fa1\u3067\u306f\u306a\u3044\u3002<\/span>\r\n  <span class=\"c1\">\/\/ \u305d\u306e\u305f\u3081\u3001\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304c\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u308b\u3002<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">handleClick<\/span> <span class=\"o\">=<\/span> <span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">click<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"p\">};<\/span>\r\n\r\n  <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n    <span class=\"p\">&lt;&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>Counter: <span class=\"si\">{<\/span><span class=\"nx\">count<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount<\/span><span class=\"p\">(<\/span><span class=\"nx\">count<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Increment count<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nc\">Child<\/span> <span class=\"na\">handleClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"nx\">handleClick<\/span><span class=\"si\">}<\/span> <span class=\"p\">\/&gt;<\/span>\r\n    <span class=\"p\">&lt;\/&gt;<\/span>\r\n  <span class=\"p\">);<\/span>\r\n<span class=\"p\">}<\/span>\r\n<\/code><\/pre>\n<p>\u5982\u679c\u5f15\u7528\u4e0d\u540c\u7684\u51fd\u6570\uff0c\u5219\u4f1a\u6210\u4e3a\u53e6\u4e00\u4e2a\u5bf9\u8c61\u3002<\/p>\n<pre class=\"post-pre\"><code><span class=\"kd\">function<\/span> <span class=\"nf\">doSomething<\/span><span class=\"p\">()<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">doSomething<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n<span class=\"p\">}<\/span>\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">func1<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">doSomething<\/span><span class=\"p\">;<\/span>\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">func2<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">doSomething<\/span><span class=\"p\">;<\/span>\r\n<span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"nx\">doSomething<\/span> <span class=\"o\">===<\/span> <span class=\"nx\">doSomething<\/span><span class=\"p\">);<\/span> <span class=\"c1\">\/\/ true<\/span>\r\n<span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"nx\">func1<\/span> <span class=\"o\">===<\/span> <span class=\"nx\">func2<\/span><span class=\"p\">);<\/span> <span class=\"c1\">\/\/ true<\/span>\r\n\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">func3<\/span> <span class=\"o\">=<\/span> <span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">doSomething<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n<span class=\"p\">};<\/span>\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">func4<\/span> <span class=\"o\">=<\/span> <span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">doSomething<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n<span class=\"p\">};<\/span>\r\n<span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"nx\">func3<\/span> <span class=\"o\">===<\/span> <span class=\"nx\">func4<\/span><span class=\"p\">);<\/span> <span class=\"c1\">\/\/ false<\/span>\r\n<\/code><\/pre>\n<p>\u7531\u4e8eApp\u7ec4\u4ef6\u6bcf\u6b21\u91cd\u65b0\u6e32\u67d3\u65f6\uff0c\u524d\u8ff0\u7684handleClick\u6240\u5f15\u7528\u7684\u51fd\u6570\u4e5f\u4f1a\u88ab\u91cd\u65b0\u751f\u6210\uff0c\u56e0\u6b64\u5b83\u4eec\u5e76\u4e0d\u662f\u7b49\u4ef7\u7684\u3002<\/p>\n<p>\u56e0\u6b64\uff0c\u5373\u4f7f\u51fd\u6570\u5185\u5bb9\u76f8\u540c\uff0cChild\u7ec4\u4ef6\u4e5f\u4f1a\u91cd\u65b0\u6e32\u67d3\u3002<\/p>\n<p>\u4e3a\u4e86\u89e3\u51b3\u8fd9\u4e2a\u95ee\u9898\uff0c\u6211\u4eec\u9700\u8981\u4f7f\u7528useCallback\u6765\u5bf9\u51fd\u6570\u8fdb\u884c\u8bb0\u5fc6\u5316\u3002<\/p>\n<h2>\u4f7f\u7528\u56de\u8c03\u51fd\u6570<\/h2>\n<p>\u8fd4\u56de\u4e00\u4e2a\u5b58\u50a8\u4e86\u56de\u8c03\u51fd\u6570\u7684\u94a9\u5b50\u3002<\/p>\n<h3>\u4e3a\u4ec0\u4e48\u8981\u4f7f\u7528 useCallback\uff1f<\/h3>\n<p>\u7531\u4e8e\u53ef\u4ee5\u4e0eReact.memo\u540c\u65f6\u4f7f\u7528\uff0c\u56e0\u6b64\u53ef\u4ee5\u8df3\u8fc7\u7ec4\u4ef6\u7684\u4e0d\u5fc5\u8981\u91cd\u65b0\u6e32\u67d3\u3002<\/p>\n<p>\u66f4\u5177\u9ad4\u5730\u8aaa\uff0c\u901a\u904e\u5c07\u4f7f\u7528useCallback\u9032\u884c\u8a18\u61b6\u5316\u7684\u56de\u8abf\u51fd\u6578\u4f5c\u70baProps\u50b3\u905e\u7d66\u4f7f\u7528React.memo\u9032\u884c\u8a18\u61b6\u5316\u7684\u7d44\u4ef6\uff0c\u53ef\u4ee5\u8df3\u904e\u7d44\u4ef6\u7684\u4e0d\u5fc5\u8981\u91cd\u65b0\u6e32\u67d3\u3002<\/p>\n<h3>\u4f7f\u7528 useCallback \u7684\u8bed\u6cd5\u3002<\/h3>\n<pre class=\"post-pre\"><code><span class=\"nf\">useCallback<\/span><span class=\"p\">(<\/span><span class=\"nx\">\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u95a2\u6570<\/span><span class=\"p\">,<\/span> <span class=\"nx\">\u4f9d\u5b58\u914d\u5217<\/span><span class=\"p\">);<\/span>\r\n<\/code><\/pre>\n<p>\u4f9d\u5b58\u6570\u7ec4\u6307\u7684\u662f\u5b58\u50a8\u4e86\u56de\u8c03\u51fd\u6570\u6240\u4f9d\u8d56\u7684\u5143\u7d20\u7684\u6570\u7ec4\u3002<\/p>\n<p>\u5982\u679c\u60f3\u8981\u5c06\u4e00\u4e2a\u8bb0\u5fc6\u5316\u51fd\u6570\u5e94\u7528\u5728\u9700\u8981\u5728console.log\u4e2d\u8f93\u51fa\u53d8\u91cfcount\u7684\u51fd\u6570\u4e2d\uff0c\u53ef\u4ee5\u6309\u7167\u4ee5\u4e0b\u65b9\u5f0f\u5b9e\u73b0\u3002<\/p>\n<pre class=\"post-pre\"><code><span class=\"kd\">const<\/span> <span class=\"nx\">callback<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useCallback<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"nx\">count<\/span><span class=\"p\">),<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count<\/span><span class=\"p\">]);<\/span>\r\n<\/code><\/pre>\n<p>\u5982\u679c\u4f9d\u5b58\u5143\u7d20\u66f4\u65b0\uff0c\u51fd\u6570\u5c06\u88ab\u91cd\u65b0\u751f\u6210\u3002<\/p>\n<p>\u5982\u679c\u6ca1\u6709\u4efb\u4f55\u4f9d\u8d56\u5143\u7d20\uff0c\u90a3\u4e48\u4f9d\u8d56\u6570\u7ec4\u53ef\u4ee5\u4e3a\u7a7a\u3002<\/p>\n<pre class=\"post-pre\"><code><span class=\"kd\">const<\/span> <span class=\"nx\">callback<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useCallback<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">doSomething<\/span><span class=\"dl\">\"<\/span><span class=\"p\">),<\/span> <span class=\"p\">[]);<\/span>\r\n<\/code><\/pre>\n<h3>\u4f7f\u7528 useCallback \u7684\u793a\u4f8b<\/h3>\n<div><img decoding=\"async\" class=\"post-images\" title=\"\" src=\"https:\/\/cdn.silicloud.com\/blog-img\/blog\/img\/657d356037434c4406c6c4a2\/77-0.gif\" alt=\"using-usecallback.gif\" \/><\/div>\n<pre class=\"post-pre\"><code><span class=\"k\">import<\/span> <span class=\"nx\">React<\/span><span class=\"p\">,<\/span> <span class=\"p\">{<\/span> <span class=\"nx\">useState<\/span><span class=\"p\">,<\/span> <span class=\"nx\">useCallback<\/span> <span class=\"p\">}<\/span> <span class=\"k\">from<\/span> <span class=\"dl\">\"<\/span><span class=\"s2\">react<\/span><span class=\"dl\">\"<\/span><span class=\"p\">;<\/span>\r\n\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">Child<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">React<\/span><span class=\"p\">.<\/span><span class=\"nf\">memo<\/span><span class=\"p\">(<\/span><span class=\"nx\">props<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render Child<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"k\">return<\/span> <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"nx\">props<\/span><span class=\"p\">.<\/span><span class=\"nx\">handleClick<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Child<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;;<\/span>\r\n<span class=\"p\">});<\/span>\r\n\r\n<span class=\"k\">export<\/span> <span class=\"k\">default<\/span> <span class=\"kd\">function<\/span> <span class=\"nf\">App<\/span><span class=\"p\">()<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render App<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"c1\">\/\/ \u95a2\u6570\u3092\u30e1\u30e2\u5316\u3059\u308c\u3070\u3001\u65b0\u3057\u3044 handleClick \u3068\u524d\u56de\u306e handleClick \u306f<\/span>\r\n  <span class=\"c1\">\/\/ \u7b49\u4fa1\u306b\u306a\u308b\u3002\u305d\u306e\u305f\u3081\u3001Child \u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306f\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u306a\u3044\u3002<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">handleClick<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useCallback<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">click<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"p\">},<\/span> <span class=\"p\">[]);<\/span>\r\n\r\n  <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n    <span class=\"p\">&lt;&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>Counter: <span class=\"si\">{<\/span><span class=\"nx\">count<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount<\/span><span class=\"p\">(<\/span><span class=\"nx\">count<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Increment count<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nc\">Child<\/span> <span class=\"na\">handleClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"nx\">handleClick<\/span><span class=\"si\">}<\/span> <span class=\"p\">\/&gt;<\/span>\r\n    <span class=\"p\">&lt;\/&gt;<\/span>\r\n  <span class=\"p\">);<\/span>\r\n<span class=\"p\">}<\/span>\r\n<\/code><\/pre>\n<h3>useCallback \u7684\u6ce8\u610f\u4e8b\u9879<\/h3>\n<p>\u7531\u4e8euseCallback\u5fc5\u987b\u4e0eReact.memo\u4e00\u8d77\u4f7f\u7528\uff0c\u56e0\u6b64\u4ee5\u4e0b\u7528\u6cd5\u662f\u65e0\u610f\u4e49\u7684\uff08\u65e0\u6cd5\u8df3\u8fc7\u7ec4\u4ef6\u7684\u4e0d\u5fc5\u8981\u91cd\u65b0\u6e32\u67d3\uff09\uff0c\u8bf7\u6ce8\u610f\u3002<\/p>\n<p>React.memo\u3067\u30e1\u30e2\u5316\u3092\u3057\u3066\u3044\u306a\u3044\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306buseCallback\u3067\u30e1\u30e2\u5316\u3092\u3057\u305f\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u95a2\u6570\u3092\u6e21\u3059<\/p>\n<p>useCallback\u3067\u30e1\u30e2\u5316\u3057\u305f\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u95a2\u6570\u3092\u3001\u305d\u308c\u3092\u751f\u6210\u3057\u305f\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u81ea\u8eab\u3067\u5229\u7528\u3059\u308b<\/p>\n<h4>\u5c06\u672a\u4f7f\u7528React.memo\u8fdb\u884c\u8bb0\u5fc6\u5316\u7684\u7ec4\u4ef6\uff0c\u901a\u8fc7useCallback\u4f20\u9012\u8bb0\u5fc6\u5316\u7684\u56de\u8c03\u51fd\u6570\u3002<\/h4>\n<p>\u5373\u4f7f\u5411\u672a\u8fdb\u884c\u8bb0\u5fc6\u5316\u7684\u7ec4\u4ef6\u4f20\u9012\u4e86\u4e00\u4e2a\u8bb0\u5fc6\u5316\u7684\u56de\u8c03\u51fd\u6570\uff0c\u8be5\u7ec4\u4ef6\u4ecd\u7136\u4f1a\u88ab\u4e0d\u65ad\u91cd\u65b0\u6e32\u67d3\u3002<\/p>\n<pre class=\"post-pre\"><code><span class=\"k\">import<\/span> <span class=\"nx\">React<\/span><span class=\"p\">,<\/span> <span class=\"p\">{<\/span> <span class=\"nx\">useState<\/span><span class=\"p\">,<\/span> <span class=\"nx\">useCallback<\/span> <span class=\"p\">}<\/span> <span class=\"k\">from<\/span> <span class=\"dl\">\"<\/span><span class=\"s2\">react<\/span><span class=\"dl\">\"<\/span><span class=\"p\">;<\/span>\r\n\r\n<span class=\"c1\">\/\/ React.memo \u3067\u30e1\u30e2\u5316\u3092\u3057\u3066\u3044\u306a\u3044\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u306e\u305f\u3081\u3001\u30e1\u30e2\u5316\u3055\u308c\u305f\u30b3\u30fc\u30eb\u30d0\u30c3\u30af\u95a2\u6570\u3092\u6e21\u3055\u308c\u3066\u3082\u610f\u5473\u304c\u306a\u3044\u3002<\/span>\r\n<span class=\"c1\">\/\/ App \u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304c\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u308b\u5ea6\u306b\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u308b\u3002<\/span>\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">Child<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">props<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render Child<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"k\">return<\/span> <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"nx\">props<\/span><span class=\"p\">.<\/span><span class=\"nx\">handleClick<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Child<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;;<\/span>\r\n<span class=\"p\">};<\/span>\r\n\r\n<span class=\"k\">export<\/span> <span class=\"k\">default<\/span> <span class=\"kd\">function<\/span> <span class=\"nf\">App<\/span><span class=\"p\">()<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render App<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">handleClick<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useCallback<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">click<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"p\">},<\/span> <span class=\"p\">[]);<\/span>\r\n\r\n  <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n    <span class=\"p\">&lt;&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>Counter: <span class=\"si\">{<\/span><span class=\"nx\">count<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount<\/span><span class=\"p\">(<\/span><span class=\"nx\">count<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Increment count<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nc\">Child<\/span> <span class=\"na\">handleClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"nx\">handleClick<\/span><span class=\"si\">}<\/span> <span class=\"p\">\/&gt;<\/span>\r\n    <span class=\"p\">&lt;\/&gt;<\/span>\r\n  <span class=\"p\">);<\/span>\r\n<span class=\"p\">}<\/span>\r\n<\/code><\/pre>\n<h4>\u5728\u751f\u6210\u4e86\u56de\u8c03\u51fd\u6570\u7684\u7ec4\u4ef6\u672c\u8eab\u4e2d\u4f7f\u7528\u4f7f\u7528useCallback\u8fdb\u884c\u8bb0\u5fc6\u7684\u56de\u8c03\u51fd\u6570\u3002<\/h4>\n<p>\u5728\u4e0b\u9762\u7684\u4f8b\u5b50\u4e2d\uff0cApp\u7ec4\u4ef6\u81ea\u8eab\u4f7f\u7528\u4e86\u7ecf\u8fc7\u8bb0\u5fc6\u5316\u7684\u56de\u8c03\u51fd\u6570\u3002<\/p>\n<p>\u867d\u7136\u8fdb\u884c\u4e86\u64cd\u4f5c\uff0c\u4f46\u5e76\u672a\u8fbe\u6210\u201c\u8df3\u8fc7\u7ec4\u4ef6\u91cd\u65b0\u6e32\u67d3\u201d\u7684\u76ee\u6807\u3002<\/p>\n<pre class=\"post-pre\"><code><span class=\"k\">import<\/span> <span class=\"nx\">React<\/span><span class=\"p\">,<\/span> <span class=\"p\">{<\/span> <span class=\"nx\">useState<\/span><span class=\"p\">,<\/span> <span class=\"nx\">useCallback<\/span> <span class=\"p\">}<\/span> <span class=\"k\">from<\/span> <span class=\"dl\">\"<\/span><span class=\"s2\">react<\/span><span class=\"dl\">\"<\/span><span class=\"p\">;<\/span>\r\n\r\n<span class=\"k\">export<\/span> <span class=\"k\">default<\/span> <span class=\"kd\">function<\/span> <span class=\"nf\">App<\/span><span class=\"p\">()<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render App<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">handleClick<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useCallback<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">memonized callback<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"p\">},<\/span> <span class=\"p\">[]);<\/span>\r\n\r\n  <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n    <span class=\"p\">&lt;&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>Counter: <span class=\"si\">{<\/span><span class=\"nx\">count<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount<\/span><span class=\"p\">(<\/span><span class=\"nx\">count<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Increment count<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"nx\">handleClick<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>logging<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n    <span class=\"p\">&lt;\/&gt;<\/span>\r\n  <span class=\"p\">);<\/span>\r\n<span class=\"p\">}<\/span>\r\n<\/code><\/pre>\n<h2>\u4f7f\u7528useMemo<\/h2>\n<p>\u8fd4\u56de\u8bb0\u5fc6\u5316\u7684\u503c\u7684\u94a9\u5b50\u51fd\u6570\u3002<\/p>\n<p>\u5728\u7ec4\u4ef6\u91cd\u65b0\u6e32\u67d3\u65f6\u53ef\u4ee5\u91cd\u65b0\u4f7f\u7528\u503c\u3002<\/p>\n<h3>\u4e3a\u4ec0\u4e48\u8981\u4f7f\u7528 useMemo\uff1f<\/h3>\n<p>\u56e0\u6b64\u53ef\u4ee5\u671f\u671b\u901a\u8fc7\u8df3\u8fc7\u4e0d\u9700\u8981\u7684\u91cd\u65b0\u8ba1\u7b97\u6765\u63d0\u9ad8\u6027\u80fd\u3002<\/p>\n<h3>useMemo \u7684\u8bed\u6cd5<\/h3>\n<pre class=\"post-pre\"><code><span class=\"nf\">useMemo<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nx\">\u5024\u3092\u8a08\u7b97\u3059\u308b\u30ed\u30b8\u30c3\u30af<\/span><span class=\"p\">,<\/span> <span class=\"nx\">\u4f9d\u5b58\u914d\u5217<\/span><span class=\"p\">);<\/span>\r\n<\/code><\/pre>\n<p>\u4f9d\u5b58\u6570\u7ec4\u662f\u4e00\u4e2a\u5b58\u50a8\u6709\u8ba1\u7b97\u903b\u8f91\u4f9d\u8d56\u7684\u5143\u7d20\uff08\u7528\u4e8e\u8ba1\u7b97\u503c\u6240\u9700\u7684\u5143\u7d20\uff09\u7684\u6570\u7ec4\u3002<\/p>\n<p>\u5982\u679c\u4f60\u60f3\u8981\u5c06\u4e00\u4e2a\u540d\u4e3a&#8221;count&#8221;\u7684\u53d8\u91cf\u7684\u503c\u52a0\u500d\u5e76\u8fdb\u884c\u7f13\u5b58\uff0c\u53ef\u4ee5\u6309\u7167\u4ee5\u4e0b\u65b9\u5f0f\u8fdb\u884c\u64cd\u4f5c\u3002<\/p>\n<pre class=\"post-pre\"><code><span class=\"kd\">const<\/span> <span class=\"nx\">result<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useMemo<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nx\">count<\/span> <span class=\"o\">*<\/span> <span class=\"mi\">2<\/span><span class=\"p\">,<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count<\/span><span class=\"p\">]);<\/span>\r\n<\/code><\/pre>\n<p>\u5982\u679c\u4f9d\u8d56\u7684\u5143\u7d20\u88ab\u66f4\u65b0\uff0c\u90a3\u4e48\u503c\u5c06\u88ab\u91cd\u65b0\u8ba1\u7b97\u3002<\/p>\n<h3>useMemo \u7684\u5e94\u7528\u793a\u4f8b<\/h3>\n<p>\u6bd4\u8f83\u4f7f\u7528useMemo\u548c\u4e0d\u4f7f\u7528useMemo\u7684\u533a\u522b\u3002<\/p>\n<h4>\u5982\u679c\u4e0d\u4f7f\u7528 useMemo<\/h4>\n<div><img decoding=\"async\" class=\"post-images\" title=\"\" src=\"https:\/\/cdn.silicloud.com\/blog-img\/blog\/img\/657d356037434c4406c6c4a2\/103-0.gif\" alt=\"unused-usememo.gif\" \/><\/div>\n<pre class=\"post-pre\"><code><span class=\"k\">import<\/span> <span class=\"nx\">React<\/span><span class=\"p\">,<\/span> <span class=\"p\">{<\/span> <span class=\"nx\">useState<\/span> <span class=\"p\">}<\/span> <span class=\"k\">from<\/span> <span class=\"dl\">\"<\/span><span class=\"s2\">react<\/span><span class=\"dl\">\"<\/span><span class=\"p\">;<\/span>\r\n\r\n<span class=\"k\">export<\/span> <span class=\"k\">default<\/span> <span class=\"kd\">function<\/span> <span class=\"nf\">App<\/span><span class=\"p\">()<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count1<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount1<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count2<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount2<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"c1\">\/\/ \u5f15\u6570\u306e\u6570\u5024\u3092\uff12\u500d\u306b\u3057\u3066\u8fd4\u3059\u3002<\/span>\r\n  <span class=\"c1\">\/\/ \u4e0d\u8981\u306a\u30eb\u30fc\u30d7\u3092\u5b9f\u884c\u3057\u3066\u3044\u308b\u305f\u3081\u8a08\u7b97\u306b\u304b\u306a\u308a\u306e\u6642\u9593\u304c\u304b\u304b\u308b\u3002<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">double<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">count<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"kd\">let<\/span> <span class=\"nx\">i<\/span> <span class=\"o\">=<\/span> <span class=\"mi\">0<\/span><span class=\"p\">;<\/span>\r\n    <span class=\"k\">while <\/span><span class=\"p\">(<\/span><span class=\"nx\">i<\/span> <span class=\"o\">&lt;<\/span> <span class=\"mi\">1000000000<\/span><span class=\"p\">)<\/span> <span class=\"nx\">i<\/span><span class=\"o\">++<\/span><span class=\"p\">;<\/span>\r\n    <span class=\"k\">return<\/span> <span class=\"nx\">count<\/span> <span class=\"o\">*<\/span> <span class=\"mi\">2<\/span><span class=\"p\">;<\/span>\r\n  <span class=\"p\">};<\/span>\r\n\r\n  <span class=\"c1\">\/\/ count2 \u3092\uff12\u500d\u306b\u3057\u305f\u5024<\/span>\r\n  <span class=\"c1\">\/\/ double(count2) \u306f\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304c\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u308b\u5ea6\u306b\u5b9f\u884c\u3055\u308c\u308b\u305f\u3081\u3001<\/span>\r\n  <span class=\"c1\">\/\/ count1 \u3092\u66f4\u65b0\u3057\u3066\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304c\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u305f\u6642\u306b\u3082\u5b9f\u884c\u3055\u308c\u3066\u3057\u307e\u3046\u3002<\/span>\r\n  <span class=\"c1\">\/\/ \u305d\u306e\u305f\u3081\u3001count1 \u3092\u66f4\u65b0\u3057\u3066\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3092\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3059\u308b\u6642\u3082\u6642\u9593\u304c\u304b\u304b\u308b\u3002<\/span>\r\n  <span class=\"c1\">\/\/ count1 \u3092\u66f4\u65b0\u3057\u3066\u3082 doubledCount \u306e\u5024\u306f\u5909\u308f\u3089\u306a\u3044\u305f\u3081\u3001count1 \u3092\u66f4\u65b0\u3057\u305f\u6642\u306b<\/span>\r\n  <span class=\"c1\">\/\/ double(count2) \u3092\u5b9f\u884c\u3059\u308b\u610f\u5473\u304c\u306a\u3044\u3002\u3057\u305f\u304c\u3063\u3066\u3001\u4e0d\u8981\u306a\u518d\u8a08\u7b97\u304c\u767a\u751f\u3057\u3066\u3044\u308b\u72b6\u614b\u3067\u3042\u308b\u3002<\/span>\r\n  <span class=\"c1\">\/\/ count1 \u304c\u66f4\u65b0\u3055\u308c\u3066\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304c\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u305f\u6642\u306f double(count2) \u304c\u5b9f\u884c\u3055\u308c\u306a\u3044\u3088\u3046\u306b\u3057\u305f\u3044\u3002<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">doubledCount<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">double<\/span><span class=\"p\">(<\/span><span class=\"nx\">count2<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n    <span class=\"p\">&lt;&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>Increment count1<span class=\"p\">&lt;\/<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>Counter: <span class=\"si\">{<\/span><span class=\"nx\">count1<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount1<\/span><span class=\"p\">(<\/span><span class=\"nx\">count1<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Increment count1<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>Increment count2<span class=\"p\">&lt;\/<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n        Counter: <span class=\"si\">{<\/span><span class=\"nx\">count2<\/span><span class=\"si\">}<\/span>, <span class=\"si\">{<\/span><span class=\"nx\">doubledCount<\/span><span class=\"si\">}<\/span>\r\n      <span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount2<\/span><span class=\"p\">(<\/span><span class=\"nx\">count2<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Increment count2<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n    <span class=\"p\">&lt;\/&gt;<\/span>\r\n  <span class=\"p\">);<\/span>\r\n<span class=\"p\">}<\/span>\r\n<\/code><\/pre>\n<p>\u5f53\u66f4\u65b0 count1 \u65f6\uff0c\u7531\u4e8e double(count2) \u4f1a\u88ab\u6267\u884c\uff0c\u56e0\u6b64\u5728\u66f4\u65b0 count1 \u5e76\u91cd\u65b0\u6e32\u67d3\u7ec4\u4ef6\u65f6\uff0c\u4f1a\u82b1\u8d39\u65f6\u95f4\u3002<\/p>\n<h4>\u5982\u679c\u4f7f\u7528useMemo\u7684\u8bdd\u3002<\/h4>\n<div><img decoding=\"async\" class=\"post-images\" title=\"\" src=\"https:\/\/cdn.silicloud.com\/blog-img\/blog\/img\/657d356037434c4406c6c4a2\/107-0.gif\" alt=\"using-usememo.gif\" \/><\/div>\n<pre class=\"post-pre\"><code><span class=\"k\">import<\/span> <span class=\"nx\">React<\/span><span class=\"p\">,<\/span> <span class=\"p\">{<\/span> <span class=\"nx\">useState<\/span><span class=\"p\">,<\/span> <span class=\"nx\">useMemo<\/span> <span class=\"p\">}<\/span> <span class=\"k\">from<\/span> <span class=\"dl\">\"<\/span><span class=\"s2\">react<\/span><span class=\"dl\">\"<\/span><span class=\"p\">;<\/span>\r\n\r\n<span class=\"k\">export<\/span> <span class=\"k\">default<\/span> <span class=\"kd\">function<\/span> <span class=\"nf\">App<\/span><span class=\"p\">()<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count1<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount1<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count2<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount2<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"c1\">\/\/ \u5f15\u6570\u306e\u6570\u5024\u3092\uff12\u500d\u306b\u3057\u3066\u8fd4\u3059\u3002<\/span>\r\n  <span class=\"c1\">\/\/ \u4e0d\u8981\u306a\u30eb\u30fc\u30d7\u3092\u5b9f\u884c\u3057\u3066\u3044\u308b\u305f\u3081\u8a08\u7b97\u306b\u304b\u306a\u308a\u306e\u6642\u9593\u304c\u304b\u304b\u308b\u3002<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">double<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">count<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"kd\">let<\/span> <span class=\"nx\">i<\/span> <span class=\"o\">=<\/span> <span class=\"mi\">0<\/span><span class=\"p\">;<\/span>\r\n    <span class=\"k\">while <\/span><span class=\"p\">(<\/span><span class=\"nx\">i<\/span> <span class=\"o\">&lt;<\/span> <span class=\"mi\">1000000000<\/span><span class=\"p\">)<\/span> <span class=\"nx\">i<\/span><span class=\"o\">++<\/span><span class=\"p\">;<\/span>\r\n    <span class=\"k\">return<\/span> <span class=\"nx\">count<\/span> <span class=\"o\">*<\/span> <span class=\"mi\">2<\/span><span class=\"p\">;<\/span>\r\n  <span class=\"p\">};<\/span>\r\n\r\n  <span class=\"c1\">\/\/ count2 \u3092\uff12\u500d\u306b\u3057\u305f\u5024\u3092\u30e1\u30e2\u5316\u3059\u308b\u3002<\/span>\r\n  <span class=\"c1\">\/\/ \u7b2c\uff12\u5f15\u6570\u306b count2 \u3092\u6e21\u3057\u3066\u3044\u308b\u305f\u3081\u3001count2 \u304c\u66f4\u65b0\u3055\u308c\u305f\u6642\u3060\u3051\u5024\u304c\u518d\u8a08\u7b97\u3055\u308c\u308b\u3002<\/span>\r\n  <span class=\"c1\">\/\/ count1 \u304c\u66f4\u65b0\u3055\u308c\u3001\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304c\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u305f\u6642\u306f\u30e1\u30e2\u5316\u3057\u305f\u5024\u3092\u5229\u7528\u3059\u308b\u305f\u3081\u518d\u8a08\u7b97\u3055\u308c\u306a\u3044\u3002<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">doubledCount<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useMemo<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">double<\/span><span class=\"p\">(<\/span><span class=\"nx\">count2<\/span><span class=\"p\">),<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count2<\/span><span class=\"p\">]);<\/span>\r\n\r\n  <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n    <span class=\"p\">&lt;&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>Increment(fast)<span class=\"p\">&lt;\/<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>Counter: <span class=\"si\">{<\/span><span class=\"nx\">count1<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount1<\/span><span class=\"p\">(<\/span><span class=\"nx\">count1<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Increment(fast)<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>Increment(slow)<span class=\"p\">&lt;\/<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n        Counter: <span class=\"si\">{<\/span><span class=\"nx\">count2<\/span><span class=\"si\">}<\/span>, <span class=\"si\">{<\/span><span class=\"nx\">doubledCount<\/span><span class=\"si\">}<\/span>\r\n      <span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount2<\/span><span class=\"p\">(<\/span><span class=\"nx\">count2<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Increment(slow)<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n    <span class=\"p\">&lt;\/&gt;<\/span>\r\n  <span class=\"p\">);<\/span>\r\n<span class=\"p\">}<\/span>\r\n<\/code><\/pre>\n<p>\u901a\u8fc7\u4f7f\u7528useMemo\uff0c\u5c06\u503c\u8fdb\u884c\u4e86\u8bb0\u5fc6\u5316\u5904\u7406\uff0c\u56e0\u6b64\u5728\u66f4\u65b0count1\u65f6\uff0c\u4e0d\u4f1a\u518d\u6267\u884cdouble(count2)\u3002<\/p>\n<p>\u56e0\u6b64\uff0c\u5f53\u66f4\u65b0count1\u65f6\uff0c\u7ec4\u4ef6\u7684\u91cd\u65b0\u6e32\u67d3\u53d8\u5f97\u66f4\u52a0\u5feb\u901f\u3002<\/p>\n<h4>\u8df3\u8fc7\u7ec4\u4ef6\u7684\u91cd\u65b0\u6e32\u67d3<\/h4>\n<p>\u7531\u4e8euseMemo\u53ef\u4ee5\u5bf9\u6e32\u67d3\u7ed3\u679c\u8fdb\u884c\u8bb0\u5fc6\uff0c\u56e0\u6b64\u53ef\u4ee5\u50cfReact.memo\u4e00\u6837\u8df3\u8fc7\u7ec4\u4ef6\u7684\u91cd\u65b0\u6e32\u67d3\u3002<\/p>\n<div><img decoding=\"async\" class=\"post-images\" title=\"\" src=\"https:\/\/cdn.silicloud.com\/blog-img\/blog\/img\/657d356037434c4406c6c4a2\/113-0.gif\" alt=\"usememo-02.gif\" \/><\/div>\n<pre class=\"post-pre\"><code><span class=\"k\">import<\/span> <span class=\"nx\">React<\/span><span class=\"p\">,<\/span> <span class=\"p\">{<\/span> <span class=\"nx\">useState<\/span><span class=\"p\">,<\/span> <span class=\"nx\">useMemo<\/span> <span class=\"p\">}<\/span> <span class=\"k\">from<\/span> <span class=\"dl\">\"<\/span><span class=\"s2\">react<\/span><span class=\"dl\">\"<\/span><span class=\"p\">;<\/span>\r\n\r\n<span class=\"k\">export<\/span> <span class=\"k\">default<\/span> <span class=\"kd\">function<\/span> <span class=\"nf\">App<\/span><span class=\"p\">()<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render App<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count1<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount1<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count2<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount2<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"c1\">\/\/ \u5f15\u6570\u306e\u6570\u5024\u3092\uff12\u500d\u306b\u3057\u3066\u8fd4\u3059\u3002<\/span>\r\n  <span class=\"c1\">\/\/ \u7121\u99c4\u306a\u30eb\u30fc\u30d7\u3092\u5b9f\u884c\u3057\u3066\u3044\u308b\u305f\u3081\u8a08\u7b97\u306b\u304b\u306a\u308a\u306e\u6642\u9593\u304c\u304b\u304b\u308b\u3002<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">double<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">count<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"kd\">let<\/span> <span class=\"nx\">i<\/span> <span class=\"o\">=<\/span> <span class=\"mi\">0<\/span><span class=\"p\">;<\/span>\r\n    <span class=\"k\">while <\/span><span class=\"p\">(<\/span><span class=\"nx\">i<\/span> <span class=\"o\">&lt;<\/span> <span class=\"mi\">1000000000<\/span><span class=\"p\">)<\/span> <span class=\"nx\">i<\/span><span class=\"o\">++<\/span><span class=\"p\">;<\/span>\r\n    <span class=\"k\">return<\/span> <span class=\"nx\">count<\/span> <span class=\"o\">*<\/span> <span class=\"mi\">2<\/span><span class=\"p\">;<\/span>\r\n  <span class=\"p\">};<\/span>\r\n\r\n  <span class=\"c1\">\/\/ \u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u7d50\u679c\uff08\u8a08\u7b97\u7d50\u679c\uff09\u3092\u30e1\u30e2\u5316\u3059\u308b<\/span>\r\n  <span class=\"c1\">\/\/ \u7b2c\uff12\u5f15\u6570\u306b count2 \u3092\u6e21\u3057\u3066\u3044\u308b\u305f\u3081\u3001count2 \u304c\u66f4\u65b0\u3055\u308c\u305f\u6642\u3060\u3051\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u308b\u3002<\/span>\r\n  <span class=\"c1\">\/\/ count1 \u304c\u66f4\u65b0\u3055\u308c\u3001\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304c\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u305f\u6642\u306f\u30e1\u30e2\u5316\u3057\u305f\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u7d50\u679c\u3092<\/span>\r\n  <span class=\"c1\">\/\/ \u5229\u7528\u3059\u308b\u305f\u3081\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u306a\u3044\u3002<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">Counter<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useMemo<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render Counter<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n    <span class=\"kd\">const<\/span> <span class=\"nx\">doubledCount<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">double<\/span><span class=\"p\">(<\/span><span class=\"nx\">count2<\/span><span class=\"p\">);<\/span>\r\n\r\n    <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n        Counter: <span class=\"si\">{<\/span><span class=\"nx\">count2<\/span><span class=\"si\">}<\/span>, <span class=\"si\">{<\/span><span class=\"nx\">doubledCount<\/span><span class=\"si\">}<\/span>\r\n      <span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n    <span class=\"p\">);<\/span>\r\n  <span class=\"p\">},<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count2<\/span><span class=\"p\">]);<\/span>\r\n\r\n  <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n    <span class=\"p\">&lt;&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>Increment count1<span class=\"p\">&lt;\/<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>Counter: <span class=\"si\">{<\/span><span class=\"nx\">count1<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount1<\/span><span class=\"p\">(<\/span><span class=\"nx\">count1<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Increment count1<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>Increment count2<span class=\"p\">&lt;\/<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"si\">{<\/span><span class=\"nx\">Counter<\/span><span class=\"si\">}<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount2<\/span><span class=\"p\">(<\/span><span class=\"nx\">count2<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Increment count2<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n    <span class=\"p\">&lt;\/&gt;<\/span>\r\n  <span class=\"p\">);<\/span>\r\n<span class=\"p\">}<\/span>\r\n<\/code><\/pre>\n<p>\u5982\u679c\u5728\u51fd\u6570\u7ec4\u4ef6\u4e2d\u60f3\u8981\u5bf9\u7ec4\u4ef6\u8fdb\u884c\u8bb0\u5fc6\uff0c\u53ef\u4ee5\u4f7f\u7528useMemo\u3002<\/p>\n<div><img decoding=\"async\" class=\"post-images\" title=\"\" src=\"https:\/\/cdn.silicloud.com\/blog-img\/blog\/img\/657d356037434c4406c6c4a2\/116-0.gif\" alt=\"meaningless-reactmemo.gif\" \/><\/div>\n<pre class=\"post-pre\"><code><span class=\"k\">import<\/span> <span class=\"nx\">React<\/span><span class=\"p\">,<\/span> <span class=\"p\">{<\/span> <span class=\"nx\">useState<\/span> <span class=\"p\">}<\/span> <span class=\"k\">from<\/span> <span class=\"dl\">\"<\/span><span class=\"s2\">react<\/span><span class=\"dl\">\"<\/span><span class=\"p\">;<\/span>\r\n\r\n<span class=\"k\">export<\/span> <span class=\"k\">default<\/span> <span class=\"kd\">function<\/span> <span class=\"nf\">App<\/span><span class=\"p\">()<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render App<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count1<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount1<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count2<\/span><span class=\"p\">,<\/span> <span class=\"nx\">setCount2<\/span><span class=\"p\">]<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useState<\/span><span class=\"p\">(<\/span><span class=\"mi\">0<\/span><span class=\"p\">);<\/span>\r\n\r\n  <span class=\"c1\">\/\/ \u5f15\u6570\u306e\u6570\u5024\u3092\uff12\u500d\u306b\u3057\u3066\u8fd4\u3059\u3002<\/span>\r\n  <span class=\"c1\">\/\/ \u7121\u99c4\u306a\u30eb\u30fc\u30d7\u3092\u5b9f\u884c\u3057\u3066\u3044\u308b\u305f\u3081\u8a08\u7b97\u306b\u304b\u306a\u308a\u306e\u6642\u9593\u304c\u304b\u304b\u308b\u3002<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">double<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">count<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"kd\">let<\/span> <span class=\"nx\">i<\/span> <span class=\"o\">=<\/span> <span class=\"mi\">0<\/span><span class=\"p\">;<\/span>\r\n    <span class=\"k\">while <\/span><span class=\"p\">(<\/span><span class=\"nx\">i<\/span> <span class=\"o\">&lt;<\/span> <span class=\"mi\">1000000000<\/span><span class=\"p\">)<\/span> <span class=\"nx\">i<\/span><span class=\"o\">++<\/span><span class=\"p\">;<\/span>\r\n    <span class=\"k\">return<\/span> <span class=\"nx\">count<\/span> <span class=\"o\">*<\/span> <span class=\"mi\">2<\/span><span class=\"p\">;<\/span>\r\n  <span class=\"p\">};<\/span>\r\n\r\n  <span class=\"c1\">\/\/ App \u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u304c\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u305f\u3089<\/span>\r\n  <span class=\"c1\">\/\/ \u3053\u306e\u30b3\u30f3\u30dd\u30fc\u30cd\u30f3\u30c8\u3082\u5fc5\u305a\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3055\u308c\u308b<\/span>\r\n  <span class=\"kd\">const<\/span> <span class=\"nx\">Counter<\/span> <span class=\"o\">=<\/span> <span class=\"nx\">React<\/span><span class=\"p\">.<\/span><span class=\"nf\">memo<\/span><span class=\"p\">(<\/span><span class=\"nx\">props<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n    <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"dl\">\"<\/span><span class=\"s2\">render Counter<\/span><span class=\"dl\">\"<\/span><span class=\"p\">);<\/span>\r\n    <span class=\"kd\">const<\/span> <span class=\"nx\">doubledCount<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">double<\/span><span class=\"p\">(<\/span><span class=\"nx\">props<\/span><span class=\"p\">.<\/span><span class=\"nx\">count2<\/span><span class=\"p\">);<\/span>\r\n\r\n    <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n        Counter: <span class=\"si\">{<\/span><span class=\"nx\">props<\/span><span class=\"p\">.<\/span><span class=\"nx\">count2<\/span><span class=\"si\">}<\/span>, <span class=\"si\">{<\/span><span class=\"nx\">doubledCount<\/span><span class=\"si\">}<\/span>\r\n      <span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n    <span class=\"p\">);<\/span>\r\n  <span class=\"p\">});<\/span>\r\n\r\n  <span class=\"k\">return <\/span><span class=\"p\">(<\/span>\r\n    <span class=\"p\">&lt;&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>Increment count1<span class=\"p\">&lt;\/<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>Counter: <span class=\"si\">{<\/span><span class=\"nx\">count1<\/span><span class=\"si\">}<\/span><span class=\"p\">&lt;\/<\/span><span class=\"nt\">p<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount1<\/span><span class=\"p\">(<\/span><span class=\"nx\">count1<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Increment count1<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>Increment count2<span class=\"p\">&lt;\/<\/span><span class=\"nt\">h2<\/span><span class=\"p\">&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nc\">Counter<\/span> <span class=\"na\">count2<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"nx\">count2<\/span><span class=\"si\">}<\/span> <span class=\"p\">\/&gt;<\/span>\r\n      <span class=\"p\">&lt;<\/span><span class=\"nt\">button<\/span> <span class=\"na\">onClick<\/span><span class=\"p\">=<\/span><span class=\"si\">{<\/span><span class=\"p\">()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nf\">setCount2<\/span><span class=\"p\">(<\/span><span class=\"nx\">count2<\/span> <span class=\"o\">+<\/span> <span class=\"mi\">1<\/span><span class=\"p\">)<\/span><span class=\"si\">}<\/span><span class=\"p\">&gt;<\/span>Increment count2<span class=\"p\">&lt;\/<\/span><span class=\"nt\">button<\/span><span class=\"p\">&gt;<\/span>\r\n    <span class=\"p\">&lt;\/&gt;<\/span>\r\n  <span class=\"p\">);<\/span>\r\n<span class=\"p\">}<\/span>\r\n<\/code><\/pre>\n<h2>\u4e3a\u4e86\u9632\u6b62\u51fd\u6570\u7684\u91cd\u65b0\u751f\u6210\uff0c\u5e94\u8be5\u4f7f\u7528useCallback\u5417\uff1f<\/h2>\n<p>\u6709\u4e9b\u4eba\u53ef\u80fd\u4f1a\u60f3\uff0c\u5982\u679c useMemo \u7528\u4e8e\u907f\u514d\u91cd\u65b0\u8ba1\u7b97\uff0c\u90a3\u4e48\u4f7f\u7528 useCallback \u4e5f\u53ef\u4ee5\u7528\u4e8e\u907f\u514d\u51fd\u6570\u7684\u91cd\u65b0\u751f\u6210\uff0c\u8fd9\u662f\u6709\u610f\u4e49\u7684\u5417\uff1f<\/p>\n<p>\u7136\u800c\uff0c\u6211\u8ba4\u4e3a\u5229\u7528\u5b83\u4f5c\u4e3a\u76ee\u7684\u662f\u4e0d\u5408\u7406\u7684\u3002<\/p>\n<p>\u56e0\u4e3a\u6211\u8ba4\u4e3a\u201c\u51fd\u6570\u91cd\u65b0\u751f\u6210\u7684\u6210\u672c\u6c38\u8fdc\u5927\u4e8euseCallback\u7684\u6267\u884c\u6210\u672c\u201d\u3002<\/p>\n<p>\u65e0\u8bba\u662fuseCallback\u8fd8\u662fuseMemo\uff0c\u5bf9\u4e8e\u8fdb\u884c\u8bb0\u5fc6\u5316\u5904\u7406\u672c\u8eab\u90fd\u6709\u6210\u672c\u3002<\/p>\n<h3>\u5728\u4f7f\u7528 useMemo \u7684\u60c5\u51b5\u4e0b<\/h3>\n<p>\u5bf9\u4e8e useMemo\uff0c\u6211\u610f\u8bc6\u5230\u6709\u65f6\u5019 &#8220;\u91cd\u65b0\u8ba1\u7b97\u7684\u6210\u672c &lt; useMemo\u7684\u6267\u884c\u6210\u672c&#8221;\uff0c\u4f46\u4e5f\u6709\u65f6\u5019 &#8220;\u91cd\u65b0\u8ba1\u7b97\u7684\u6210\u672c &gt; useMemo\u7684\u6267\u884c\u6210\u672c&#8221;\u3002<\/p>\n<p>\u9019\u662f\u4e00\u500b\u6975\u7aef\u7684\u4f8b\u5b50\uff0c\u4ee5\u4e0b\u662f\u300c\u91cd\u65b0\u8a08\u7b97\u6210\u672c &lt; \u4f7f\u7528useMemo\u7684\u57f7\u884c\u6210\u672c\u300d\u7684\u5be6\u4f8b\u3002<\/p>\n<pre class=\"post-pre\"><code><span class=\"kd\">const<\/span> <span class=\"nx\">result<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useMemo<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nx\">value<\/span> <span class=\"o\">*<\/span> <span class=\"mi\">2<\/span><span class=\"p\">,<\/span> <span class=\"p\">[<\/span><span class=\"nx\">value<\/span><span class=\"p\">]);<\/span>\r\n<\/code><\/pre>\n<p>\u56e0\u4e3avalue * 2\u662f\u4e00\u4e2a\u7b80\u5355\u7684\u8ba1\u7b97\uff0c\u6240\u4ee5\u4f7f\u7528useMemo\u4e5f\u6ca1\u6709\u6548\u679c\u3002<\/p>\n<p>\u6211\u8ba4\u4e3a\uff0c\u5728\u4e0a\u8ff0\u60c5\u51b5\u4e0b\u4f7f\u7528useMemo\u53ef\u80fd\u662f\u4e0d\u5408\u7406\u7684\uff0c\u56e0\u4e3a\u5b9e\u9645\u4e0auseMemo\u7684\u6267\u884c\u6210\u672c\u53ef\u80fd\u66f4\u9ad8\u3002<\/p>\n<p>\u800c\u4e14\uff0c\u4ee5\u4e0b\u662f\u4e00\u4e2a\u5173\u4e8e\u201c\u91cd\u65b0\u8ba1\u7b97\u7684\u6210\u672c &gt; useMemo\u6267\u884c\u6210\u672c\u201d\u7684\u4f8b\u5b50\u3002<\/p>\n<pre class=\"post-pre\"><code><span class=\"kd\">const<\/span> <span class=\"nx\">result<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useMemo<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"kd\">let<\/span> <span class=\"nx\">i<\/span> <span class=\"o\">=<\/span> <span class=\"mi\">0<\/span><span class=\"p\">;<\/span>\r\n  <span class=\"k\">while <\/span><span class=\"p\">(<\/span><span class=\"nx\">i<\/span> <span class=\"o\">&lt;<\/span> <span class=\"mi\">1000000000<\/span><span class=\"p\">)<\/span> <span class=\"nx\">i<\/span><span class=\"o\">++<\/span><span class=\"p\">;<\/span>\r\n  <span class=\"nx\">count<\/span> <span class=\"o\">*<\/span> <span class=\"mi\">2<\/span><span class=\"p\">;<\/span>\r\n<span class=\"p\">},<\/span> <span class=\"p\">[<\/span><span class=\"nx\">value<\/span><span class=\"p\">]);<\/span>\r\n<\/code><\/pre>\n<p>\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u663e\u7136\u91cd\u65b0\u8ba1\u7b97\u7684\u6210\u672c\u66f4\u9ad8\uff0c\u56e0\u6b64\u4f7f\u7528useMemo\u53ef\u4ee5\u83b7\u5f97\u663e\u8457\u7684\u6548\u679c\u3002<\/p>\n<h3>\u5f53\u4f7f\u7528 useCallback \u65f6\u3002<\/h3>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e2a\u4f8b\u5b50\uff0c\u8868\u8fbe\u7684\u542b\u4e49\u662f\u201c\u91cd\u65b0\u751f\u6210\u51fd\u6570\u7684\u6210\u672c\u5c0f\u4e8e\u6267\u884cuseCallback\u7684\u6210\u672c\u201d\u3002<\/p>\n<pre class=\"post-pre\"><code><span class=\"kd\">const<\/span> <span class=\"nx\">handleClick<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useCallback<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"p\">{<\/span>\r\n  <span class=\"nx\">console<\/span><span class=\"p\">.<\/span><span class=\"nf\">log<\/span><span class=\"p\">(<\/span><span class=\"nx\">value<\/span><span class=\"p\">);<\/span>\r\n<span class=\"p\">},<\/span> <span class=\"p\">[<\/span><span class=\"nx\">value<\/span><span class=\"p\">]);<\/span>\r\n<\/code><\/pre>\n<p>\u6211\u8ba4\u4e3a\u4e0e\u524d\u9762\u63d0\u5230\u7684useMemo\u7c7b\u4f3c\uff0c\u6ca1\u6709\u5fc5\u8981\u7279\u610f\u4f7f\u7528\u5b83\u3002<\/p>\n<p>\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u6211\u65e0\u6cd5\u60f3\u8c61\u51fa\u201c\u51fd\u6570\u91cd\u65b0\u751f\u6210\u7684\u6210\u672c\u5927\u4e8euseCallback\u7684\u6267\u884c\u6210\u672c\u201d\u7684\u60c5\u51b5\u3002<\/p>\n<pre class=\"post-pre\"><code><span class=\"c1\">\/\/ ?<\/span>\r\n<\/code><\/pre>\n<p>\u6240\u4ee5\uff0c\u6211\u8ba4\u4e3a\u4f7f\u7528useCallback\u6765\u9632\u6b62\u51fd\u6570\u91cd\u65b0\u751f\u6210\u4e0d\u5408\u7406\u4e14\u6ca1\u6709\u5fc5\u8981\u3002<\/p>\n<p>\u7531\u4e8e\u6ca1\u6709\u8fdb\u884c\u4e25\u683c\u7684\u6d4b\u91cf\uff0c\u6240\u4ee5\u8fd9\u79cd\u8ba4\u8bc6\u53ef\u80fd\u662f\u9519\u8bef\u7684\u3002<\/p>\n<p>\u5982\u679c\u6211\u5bf9\u6b64\u7684\u7406\u89e3\u662f\u9519\u8bef\u7684\uff08\u5373\u5b58\u5728\u60c5\u51b5\u300c\u91cd\u65b0\u751f\u6210\u51fd\u6570\u7684\u6210\u672c &gt; \u4f7f\u7528useCallback\u7684\u6267\u884c\u6210\u672c\u300d\uff0c\u6216\u8005\u6709\u5176\u4ed6\u7528\u9014\uff09\uff0c\u8bf7\u60a8\u5e26\u4e0a\u5177\u4f53\u793a\u4f8b\uff08\u4ee3\u7801\uff09\uff0c\u5e76\u63d0\u4f9b\u610f\u89c1\u548c\u6307\u5bfc\uff0c\u8fd9\u5c06\u975e\u5e38\u6709\u5e2e\u52a9\u3002<\/p>\n<h2>\u9700\u8981\u6b63\u786e\u6307\u5b9a\u4f9d\u5b58\u6570\u7ec4\u3002<\/h2>\n<p>\u5982\u679c\u4e0d\u6b63\u786e\u5730\u6307\u5b9auseCallback\u548cuseMemo\u7684\u4f9d\u8d56\u6570\u7ec4\uff0c\u4f1a\u5bfc\u81f4\u9519\u8bef\u7684bug\u3002<\/p>\n<p>\u56e0\u6b64\uff0c\u4ee5\u4e0b\u7684\u4ee3\u7801\u662f\u9519\u8bef\u7684\u3002<\/p>\n<pre class=\"post-pre\"><code><span class=\"c1\">\/\/ \u4f9d\u5b58\u8981\u7d20\u3067\u3042\u308b count2 \u304c\u4f9d\u5b58\u914d\u5217\u306b\u306a\u3044\u305f\u3081 NG<\/span>\r\n<span class=\"kd\">const<\/span> <span class=\"nx\">result<\/span> <span class=\"o\">=<\/span> <span class=\"nf\">useMemo<\/span><span class=\"p\">(()<\/span> <span class=\"o\">=&gt;<\/span> <span class=\"nx\">count<\/span> <span class=\"o\">*<\/span> <span class=\"nx\">count2<\/span><span class=\"p\">,<\/span> <span class=\"p\">[<\/span><span class=\"nx\">count<\/span><span class=\"p\">]);<\/span>\r\n\r\n<span class=\"c1\">\/\/ \u3053\u308c\u304c\u6b63\u3057\u3044<\/span>\r\n<span class=\"c1\">\/\/ const result = useMemo(() =&gt; count * count2, [count, count2]);<\/span>\r\n<\/code><\/pre>\n<p>\u56e0\u6b64\uff0c\u4f7f\u7528eslint-plugin-react-hooks\u7b49\u5de5\u5177\u6765\u786e\u4fdd\u8fdb\u884cLint\u68c0\u67e5\u3002<\/p>\n<h2>\u7528\u9014<\/h2>\n<p>\u901a\u8fc7\u6d4b\u91cf\u6027\u80fd\uff0c\u5e76\u5c06\u5176\u5e94\u7528\u4e8e\u6210\u4e3a\u74f6\u9888\u7684\u90e8\u5206\uff0c\u662f\u6700\u6709\u6548\u7684\u65b9\u6cd5\u3002<\/p>\n<p>\u5c3d\u7ba1\u5982\u6b64\uff0c\u5728GitHub\u4e0a\u68c0\u67e5\u4e86\u4e00\u4e0b\u4ee3\u7801\u548c\u6280\u672f\u4e66\uff0c\u53d1\u73b0\u5927\u91cf\u4f7f\u7528\u3002<\/p>\n<p>\u53ea\u8981\u5bf9\u5404\u4e2a\u529f\u80fd\u548c\u89d2\u8272\u6709\u900f\u5f7b\u7684\u7406\u89e3\uff0c\u5373\u4f7f\u4e0d\u8bbe\u5b9a\u4e25\u683c\u7684\u4f7f\u7528\u6807\u51c6\uff0c\u6211\u8ba4\u4e3a\u79ef\u6781\u5229\u7528\u4e5f\u4e0d\u4f1a\u5e26\u6765\u5927\u95ee\u9898\u3002<\/p>\n<h2>\u7ed3\u675f<\/h2>\n<p>\u8fd9\u6b21\u51c6\u5907\u7684\u6f14\u793a\u867d\u7136\u662f\u6781\u7aef\u7684\u4f8b\u5b50\uff0c\u4f46\u6839\u636e\u4f7f\u7528\u573a\u666f\u6765\u770b\uff0c\u5b83\u662f\u975e\u5e38\u6709\u7528\u7684\u529f\u80fd\u3002<\/p>\n<p>\u6839\u636e\u60c5\u51b5\u6765\u4f7f\u7528\u3002<\/p>\n<p>\u5982\u679c\u4f60\u5bf9React\u611f\u5174\u8da3\uff0c\u6211\u8fd8\u5199\u4e86\u4e00\u4e9b\u4e0e\u4e4b\u76f8\u5173\u7684\u6587\u7ae0\uff0c\u5e0c\u671b\u4f60\u4e5f\u80fd\u770b\u4e00\u770b\u3002<\/p>\n<ul class=\"post-ul\">React \u306e Context \u306e\u66f4\u65b0\u306b\u3088\u308b\u4e0d\u8981\u306a\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3092\u9632\u3050 \u301cuseContext \u3092\u5229\u7528\u6642\u306b\u767a\u751f\u3059\u308b\u4e0d\u8981\u306a\u518d\u30ec\u30f3\u30c0\u30ea\u30f3\u30b0\u3092\u9632\u3050\u65b9\u6cd5\u306b\u95a2\u3057\u3066\u301c<\/ul>\n<h2>\u6d88\u606f<\/h2>\n<p>\u6211\u5728Udemy\u4e0a\u53d1\u5e03\u4e86\u6709\u5173webpack\u7684\u8bfe\u7a0b\uff0c\u8fd8\u5728Kindle\u4e0a\u51fa\u7248\u4e86\u6280\u672f\u4e66\u7c4d\u3002<\/p>\n<p>Udemy: webpack \u901f\u6210\u8bfe\u7a0b\uff08\u539f\u4ef710,800\u5186\uff0c\u73b0\u4ef72,000\u5186\uff09<\/p>\n<p>Kindle\uff08\u5982\u679c\u662fKindle Unlimited\uff0c\u90a3\u5c31\u662f\u514d\u8d39\u7684\uff09:<br \/>\nReact Hooks\u521d\u7ea7\u6307\u5357\uff08500\u65e5\u5143\uff09<\/p>\n<p>\u5982\u679c\u60a8\u5bf9\u6b64\u611f\u5230\u5174\u8da3\u5e76\u8d2d\u4e70\u7684\u8bdd\uff0c\u6211\u4f1a\u975e\u5e38\u9ad8\u5174\u3002\u8c22\u8c22\uff01<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u9996\u5148 \u4ee5\u4e0b\u662f\u5173\u4e8eReact\uff08v16.12.0\uff09\u7684React.memo\u3001useCallback\u548cuseMemo\u7684 [&hellip;]<\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-38640","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v21.5 (Yoast SEO v21.5) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>\u7406\u89e3\u548c\u4f7f\u7528 React.memo \/ useCallback \/ useMemo \u53ef\u4ee5\u8fdb\u884c\u6027\u80fd\u4f18\u5316 - Blog - Silicon Cloud<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.silicloud.com\/zh\/blog\/\u7406\u89e3\u548c\u4f7f\u7528-react-memo-usecallback-usememo-\u53ef\u4ee5\u8fdb\u884c\u6027\u80fd\u4f18\u5316\u3002\/\" \/>\n<meta property=\"og:locale\" content=\"zh_CN\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"\u7406\u89e3\u548c\u4f7f\u7528 React.memo \/ useCallback \/ useMemo \u53ef\u4ee5\u8fdb\u884c\u6027\u80fd\u4f18\u5316\" \/>\n<meta property=\"og:description\" content=\"\u9996\u5148 \u4ee5\u4e0b\u662f\u5173\u4e8eReact\uff08v16.12.0\uff09\u7684React.memo\u3001useCallback\u548cuseMemo\u7684 [&hellip;]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.silicloud.com\/zh\/blog\/\u7406\u89e3\u548c\u4f7f\u7528-react-memo-usecallback-usememo-\u53ef\u4ee5\u8fdb\u884c\u6027\u80fd\u4f18\u5316\u3002\/\" \/>\n<meta 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