{"id":207,"date":"2021-02-10T10:19:19","date_gmt":"2021-02-10T02:19:19","guid":{"rendered":"http:\/\/gjweb.top\/?p=207"},"modified":"2021-02-10T10:19:20","modified_gmt":"2021-02-10T02:19:20","slug":"hooks%e7%bb%84%e4%bb%b6%e8%af%a6%e8%a7%a3%ef%bc%88%e4%b8%8a%ef%bc%89","status":"publish","type":"post","link":"https:\/\/gjweb.top\/?p=207","title":{"rendered":"hooks\u7ec4\u4ef6\u8be6\u89e3\uff08\u4e0a\uff09"},"content":{"rendered":"\n
  1. useState\u7528\u6cd5<\/li>
  2. useREducer\u7528\u6cd5<\/li>
  3. useContent\u7528\u6cd5<\/li>
  4. useEffect & useLayoutEffect\u7684\u533a\u522b\u7528\u6cd5<\/li>
  5. useMemo && React.memo && useCallback\u7528\u6cd5<\/li><\/ol>\n\n\n\n

    1.useState\u7528\u6cd5<\/h2>\n\n\n\n
    • useState\u4f7f\u7528\u72b6\u6001<\/li>
    • \u6ce8\u610f\u4e8b\u9879
      • \u4e0d\u53ef\u4ee5\u5c40\u90e8\u66f4\u65b0
        • \u5982\u679cstate\u662f\u4e00\u4e2a\u5bf9\u8c61\uff0csetState\u4e0d\u4f1a\u81ea\u52a8\u5408\u5e76\u5c5e\u6027<\/li><\/ul><\/li>
        • \u5982\u679csetState\uff08obj\uff09\u5982\u679c\u5730\u5740\u4e0d\u53d8\uff0creact\u5c31\u4f1a\u8ba4\u4e3a\u6570\u636e\u6ca1\u53d8<\/li>
        • useState\u53ef\u4ee5\u63a5\u6536\u51fd\u6570<\/li><\/ul><\/li><\/ul>\n\n\n\n
              const [state,setState] = useState(()=>{
                  return {}
              })<\/pre>\n\n\n\n
          \u6848\u4f8b<\/p>\n\n\n\n
              function App() {
                  const [user,setUser] = useState({name:'\u5c0f\u660e', age: 18})
                  const onClick = ()=>{
                      setUser({
                      ...user,
                      name: '\u5c0f\u7ea2'
                      })
                  }
                  return (
                      <div className=\"App\">
                      <h1>{user.name}<\/h1>
                      <h2>{user.age}<\/h2>
                      <button onClick={onClick}>Click<\/button>
                      <\/div>
                  );
              }<\/pre>\n\n\n\n
          2. useREducer\u7528\u6cd5<\/h2>\n\n\n\n
          • \u53ef\u4ee5\u7406\u89e3\u6210useState\u7684\u590d\u6742\u7248<\/li><\/ul>\n\n\n\n
                const initial = {
                    n: 0
                };
            \u200b
                const reducer = (state, action) => {
                    if (action.type === \"add\") {
                        return { n: state.n + action.number };
                    } else if (action.type === \"multi\") {
                        return { n: state.n * 2 };
                    } else {
                        throw new Error(\"unknown type\");
                    }
                };
            \u200b
                function App() {
                    const [state, dispatch] = useReducer(reducer, initial);
                    const { n } = state;
                    const onClick = () => {
                        dispatch({ type: \"add\", number: 1 });
                    };
                    const onClick2 = () => {
                        dispatch({ type: \"add\", number: 2 });
                    };
                    return (
                        <div className=\"App\">
                        <h1>n: {n}<\/h1>
            \u200b
                        <button onClick={onClick}>+1<\/button>
                        <button onClick={onClick2}>+2<\/button>
                        <\/div>
                    );
                }<\/pre>\n\n\n\n
            3. useContent\u7528\u6cd5<\/h2>\n\n\n\n
            • useContent\u5168\u5c40\u53d8\u91cf\u662f\u5168\u5c40\u7684\u4e0a\u4e0b\u6587<\/li>
            • \u6ce8\u610f
              • \u4e0d\u662f\u54cd\u5e94\u5f0f\u7684
                • \u5728\u4e00\u4e2a\u6a21\u5757\u5c06C\u91cc\u9762\u7684\u503c\u6539\u53d8\u540e\uff0c\u53e6\u4e00\u4e2a\u6a21\u5757\u4e0d\u4f1a\u611f\u77e5\u8fd9\u4e2a\u53d8\u5316<\/li><\/ul><\/li><\/ul><\/li><\/ul>\n\n\n\n
                      const C = createContext(null);
                  \u200b
                      function App() {
                          console.log(\"App \u6267\u884c\u4e86\");
                          const [n, setN] = useState(0);
                          return (
                              <C.Provider value={{ n, setN }}>
                              <div className=\"App\">
                                  <Baba \/>
                              <\/div>
                              <\/C.Provider>
                          );
                      }
                  \u200b
                      function Baba() {
                          const { n, setN } = useContext(C);
                          return (
                              <div>
                              \u6211\u662f\u7238\u7238 n: {n} <Child \/>
                              <\/div>
                          );
                      }
                  \u200b
                      function Child() {
                          const { n, setN } = useContext(C);
                          const onClick = () => {
                              setN(i => i + 1);
                          };
                          return (
                              <div>
                              \u6211\u662f\u513f\u5b50 \u6211\u5f97\u5230\u7684 n: {n}
                              <button onClick={onClick}>+1<\/button>
                              <\/div>
                          );
                      }<\/pre>\n\n\n\n
                  4. useEffect & useLayoutEffect\u7684\u533a\u522b\u7528\u6cd5<\/h2>\n\n\n\n
                  • useEffect \u526f\u4f5c\u7528
                    • \u5bf9\u73af\u5883\u7684\u6539\u53d8\u5c31\u662f\u526f\u4f5c\u7528,\u5982\u4fee\u6539\u4e86document.title<\/li><\/ul><\/li>
                    • \u7528\u9014
                      • \u5728\u51fd\u6570\u7ec4\u4ef6\u4e2d\u6a21\u62dfcomponentDidMount\\componentDidUpdate\\componentWillUnmount<\/li>
                      • \u4ee5\u4e0a\u4e09\u79cd\u7528\u9014\u53ef\u4ee5\u540c\u65f6\u5b58\u5728<\/li><\/ul><\/li>
                      • \u5f53\u591a\u4e2auseEffect\u51fa\u73b0\u65f6,\u4f1a\u6309\u7167\u51fa\u73b0\u7684\u6b21\u5e8f\u6267\u884c<\/li><\/ul>\n\n\n\n
                            function App(){
                                const [n,setN] = useState(0)
                                const add = ()=>{
                                    setN((state)=>{return state+1})
                                }
                                useEffect(()=>{
                                    console.log(\"\u7b2c\u4e00\u6b21\u6e32\u67d3\u6267\u884c\")
                                },[])
                                useEffect(()=>{
                                    console.log(\"n\u53d1\u751f\u53d8\u5316\u662f\u6267\u884c\")
                                },[n])
                                useEffect(()=>{
                                    return ()=>{
                                        console.log(\"\u9875\u9762\u9500\u6bc1\u65f6\u6267\u884c\")
                                    }
                                },[])
                                return(
                                    <div>
                                        {n}
                                        <button onClick={add}>add<\/button>
                                    <\/div>
                                )
                            }<\/pre>\n\n\n\n
                        useLayoutEffect<\/h3>\n\n\n\n
                        \u7528\u6cd5\u548cuseEffect\u5b8c\u5168\u76f8\u540c \u6848\u4f8b\u4e00<\/p>\n\n\n\n
                            const App = () => {
                                const [value, setValue] = useState(0);
                        \u200b
                                useEffect(() => {
                                    document.querySelector(\"#x\").innerText = `value: 1000`;
                                }, [value]);
                        \u200b
                                return (
                                    <div id=\"x\" onClick={() => setValue(0)}>
                                        value: {value}
                                    <\/div>
                                );
                            };<\/pre>\n\n\n\n
                        \u4e0a\u9762\u7684\u4ee3\u7801\u4f1a\u5728\u4f1a\u6d4f\u89c8\u5668\u5f00\u59cb\u663e\u793avalue:0,\u7136\u540e\u5728\u663e\u793avalue:100;(\u5982\u679c\u60f3\u8ba9\u6d4f\u89c8\u5668\u76f4\u63a5\u663e\u793avalue:100)<\/p>\n\n\n\n
                            useLayoutEffect(() => {
                                document.querySelector(\"#x\").innerText = `value: 1000`;
                            }, [value]);<\/pre>\n\n\n\n
                        useEffect\u548cuseLayoutEffect\u7684\u533a\u522b<\/h3>\n\n\n\n
                        • useEffect\u5728render\u4e4b\u540e\u6267\u884c,\u6240\u4ee5\u9875\u9762\u4f1a\u5148\u663e\u793avalue:0\u7136\u540e\u5728\u66f4\u65b0\u4e3avalue:1000<\/li>
                        • useLayoutEffects\u5728render\u4e4b\u524d\u6267\u884c,\u5728\u9875\u9762\u6e32\u67d3\u4e4b\u524dvalue\u5df2\u7ecf\u88ab\u66f4\u6539\u4e3a1000; \u56fa\u4e24\u8005\u8fd9\u7684\u533a\u522b\u5c31\u662f\u6267\u884c\u65f6\u673a\u7684\u533a\u522b,\u5728\u5f00\u53d1\u8fc7\u7a0b\u4e2d\u63a8\u8350\u4f7f\u7528useEffect<\/li><\/ul>\n\n\n\n
                          5. useMemo && React.memo && useCallback\u7528\u6cd5<\/h2>\n\n\n\n
                          • useMemo\u4e3a\u4e86\u89e3\u51b3React\u7684\u591a\u4f59\u6e32\u67d3
                            • \u573a\u666f \u5f53App\u7ec4\u4ef6\u5f15\u7528\u5b50\u7ec4\u4ef6\u65f6,\u5f53App\u7ec4\u4ef6\u66f4\u65b0\u65f6\u4f1a\u91cd\u65b0\u8c03\u7528App()\u91cd\u65b0\u5e76\u91cd\u65b0\u6e32\u67d3\u5b50\u7ec4\u4ef6,\u8fd9\u5c31\u5bfc\u81f4\u4e86\u5b50\u7ec4\u4ef6\u5728\u6ca1\u6709\u4efb\u4f55\u6539\u53d8\u5c31\u88ab\u91cd\u65b0\u6e32\u67d3\u4e86.<\/li><\/ul><\/li>
                            • useMemo \u642d\u914dReact.memo\u4f7f\u7528<\/li><\/ul>\n\n\n\n
                                  function App(){
                                  console.log(\"\u8c03\u7528\u4e86app\")
                                  const [n,setN] = useState(0)
                                  const [m,setM] = useState(0)
                                  const addN = ()=>{
                                      setN((state)=>{
                                          return state+1
                                      })
                                  }
                                  const addM = useMemo(()=>{
                                      return ()=>{
                                                  setM((state)=>{
                                                      return state+1
                                                  })
                                              }
                                  },[m])
                                  return (
                                      <div>
                                          <div>
                                              prend:{n}
                                              <button onClick={addN}>addN<\/button>
                                          <\/div>
                                          {\/*<Child2 data={m} onClick={addM}><\/Child2>*\/}
                                          <Child2 data={m} onClick={addM}><\/Child2>
                                      <\/div>
                                  )
                              \u200b
                              }
                              \u200b
                              const Child2 = React.memo((props)=>{
                                  console.log(\"\u8c03\u7528\u4e86CHild\")
                                  return(
                                      <div>
                                          Child: {props.data}
                                          <button onClick={props.onClick}>addM<\/button>
                                      <\/div>
                                  )
                              })
                              \u200b<\/pre>\n\n\n\n
                              usememo\u7684\u8bed\u6cd5\u7cd6 useCallback<\/p>\n\n\n\n
                                  \/\/useMemo\u7684\u8bed\u6cd5\u7cd6\n    const addM =useCallback(\n        ()=>{\n            setM((state)=>{\n                return state+1\n            })\n        },[m]\n    )<\/pre>\n","protected":false},"excerpt":{"rendered":"
                              useState\u7528\u6cd5 useREducer\u7528\u6cd5 useContent\u7528\u6cd5 useEffect & us […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[28],"tags":[],"class_list":["post-207","post","type-post","status-publish","format-standard","hentry","category-react"],"_links":{"self":[{"href":"https:\/\/gjweb.top\/index.php?rest_route=\/wp\/v2\/posts\/207","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gjweb.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gjweb.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gjweb.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gjweb.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=207"}],"version-history":[{"count":0,"href":"https:\/\/gjweb.top\/index.php?rest_route=\/wp\/v2\/posts\/207\/revisions"}],"wp:attachment":[{"href":"https:\/\/gjweb.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=207"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gjweb.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=207"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gjweb.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=207"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}