React 基础巩固(四十六)——自定义Hook的应用

一、自定义Hook的应用

自定义Hook本质上只是一种函数代码逻辑的抽取，严格意义上而言，它并不算React的特性。

1. 实现组件创建/销毁时打印日志

   import React, { memo, useEffect, useState } from "react";function useLogLife(name) {useEffect(() => {console.log(`${name}组件创建`);return () => {console.log(`${name}组件销毁`);};}, []);
   }const Home = memo(() => {useLogLife("Home");return <h1>Home Page</h1>;
   });const About = memo(() => {useLogLife("About");return <h1>About Page</h1>;
   });export default memo(function App() {const [isShow, setIsShow] = useState(true);useLogLife("App");return (<div><h1>App Component</h1><button onClick={(e) => setIsShow(!isShow)}>切换</button>{isShow && <Home />}{isShow && <About />}</div>);
   });

   

2. 实现Context共享

   封装TokenContext和UserContext 两个Context在自定义HookuseUserToken中，通过使用userUserToken同时获取两个Context的内容：

   import React, { memo, useContext } from "react";
   import { useUserToken } from "./hooks";const Home = memo(() => {const [user, token] = useUserToken();console.log(user, token);return <h1>Home Page</h1>;
   });const About = memo(() => {const [user, token] = useUserToken();console.log(user, token);return <h1>About Page</h1>;
   });export default memo(function App() {return (<div><h1>App Component</h1><Home /><About /></div>);
   });

   

3. 实现获取滚动位置

   封装滚动监听事件：

   import { useEffect, useState } from "react";function useScrollPosition() {const [scrollX, setScrollX] = useState(0);const [scrollY, setScrollY] = useState(0);useEffect(() => {function handleScroll() {console.log(window.scrollX, window.scrollY);setScrollX(window.scrollX);setScrollY(window.scrollY);}window.addEventListener("scroll", handleScroll);return () => {window.removeEventListener("scroll", handleScroll);};}, []);return [scrollX, scrollY];
   }export default useScrollPosition;

   通过useScrollPosition自定义Hook进行复用：

   import React, { memo } from "react";
   import "./style.css";
   import { useScrollPosition } from "./hooks";
   const Home = memo(() => {const [scrollX, scrollY] = useScrollPosition();console.log("Home", scrollX, scrollY);return (<h1>Home Page: {scrollX} --- {scrollY}</h1>);
   });const About = memo(() => {const [scrollX, scrollY] = useScrollPosition();console.log("About", scrollX, scrollY);return (<h1>About Page: {scrollX} --- {scrollY}</h1>);
   });
   export default memo(function App() {return (<div className="app"><h1>App Component</h1><Home /><About /></div>);
   });

   

4. localStorage数据存储

   封装useLocalStorage自定义Hook：

   import { useEffect, useState } from "react";function useLocalStorage(key) {const [data, setData] = useState(() => {const item = localStorage.getItem(key);if (!item) return "";return JSON.parse(item);});useEffect(() => {localStorage.setItem(key, JSON.stringify(data));}, [data]);return [data, setData];
   }
   export default useLocalStorage;

   通过useLocalStorage来实现localStorage数据的自动化存储，并进行复用。即，一旦需要本地存储的值发生变化，便对localStorage进行对应的更新：

   import React, { memo, useEffect, useState } from "react";
   import "./style.css";
   import { useLocalStorage } from "./hooks";export default memo(function App() {// 通过key，直接从localStorage获取数据const [token, setToken] = useLocalStorage("token");function setTokenHandle() {setToken("new token");}const [avatarUrl, setAvatarUrl] = useLocalStorage("avatarUrl");function setAvatarUrlHandle() {setAvatarUrl("new url");}return (<div className="app"><h1>App Component</h1><h1>token:{token}</h1><button onClick={setTokenHandle}>设置token</button><h1>Avatar:{avatarUrl}</h1><button onClick={setAvatarUrlHandle}>设置avatarUrl</button></div>);
   });