How React distinguishes components defined by Class and function-JS Tutorial-php.cn

React distinguishes components defined by Class and function: 1. Use function to define components, and add hooks to allow components defined by function to have local state; 2. Use class to define components, and filter out the second parameter of qs prefix.

How React distinguishes components defined by Class and function

The operating environment of this tutorial: Windows 7 system, React version 16.8. This method is suitable for all brands of computers.

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React distinguishes the component methods defined by Class and function:

Use function to define components

import React, { useState, useEffect } from "react"; import { useLocation } from "react-router-dom"; import qs from "qs"; //qs用来格式化数据 import { movieDetail } from "../../services/movies"; //推荐使用function定义组件,react16.8以后新增hook可以让function定义的组件具有局部state export default function Detail() { //function定义的组件没有局部的数据，所以使用useState()获取局部数据（局部状态） //以下例子第一个参数表示定义的数据，第二个参数表示更改此数据要用到的方法，useState()中的参数表示定义数据的初始值 //也就是movie={video:{}} 若要定义多个值，多次使用useState就行了 const [movie, setMovie] = useState({ video: {}, }); const [live, sertLive] = useState({}); //live={} //function定义的组件不能使用this.props.location来获取地址栏信息，使用useLocation()获取地址栏信息 const location = useLocation(); console.log(location); //function定义的组件也没有生命周期的钩子函数，我们使用useEffect来模拟生命周期, //参数一表示参数二依赖的内容发生改变之后触发的回调函数，如果参数二为空数组表示只执行一次（初始化执行） useEffect(() => { const query = qs.parse(location.search, { ignoreQueryPrefix: true, //此参数表示过滤掉前缀 }); //useEffect中调用异步函数如下所示 async function fetchData() { // You can await here const result = await movieDetail(query.id); console.log(result); setMovie(result.data.data.basic); sertLive(result.data.data.live); } fetchData(); }, []); return (   {movie.name}
 {movie.story}
  
 ); }

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Use class to define components

import React, { useState, useEffect, Component} from "react"; import { useLocation } from "react-router-dom"; import qs from "qs"; //qs用来格式化数据 import { movieDetail } from "../../services/movies"; //使用class定义组件中this指向复杂，不推荐使用 export default class Detail extends Component { constructor(props) { super(props); console.log(props); this.state = { movie: { video: { url: "", }, }, }; } async componentDidMount() { console.log(this.props.location.search); //url传参 //qs第二个参数表示过滤掉前缀 const query = qs.parse(this.props.location.search, { ignoreQueryPrefix: true, }); console.log(query); const result = await movieDetail(query.id); console.log(result); this.setState({ movie: result.data.data.basic, }); document .querySelectorAll(".nav ul li")[1] .querySelector("a") .classList.add("active"); } componentWillUnmount() { document .querySelectorAll(".nav ul li")[1] .querySelector("a") .classList.remove("active"); } render() { return (  {this.state.movie.name}
 {this.state.movie.story}
  
 ); } }

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