21-React-Custom
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在React的世界里,"21-React-Custom"可能是一个项目或者教程,专注于自定义React组件和使用钩子(Hooks)来提升应用的性能和可维护性。React是Facebook开发的一个用于构建用户界面的JavaScript库,它以其声明式编程风格和组件化特性而闻名。在React 16.8版本引入了Hooks,极大地改变了我们编写React组件的方式,使得状态管理和副作用处理更加简洁高效。 一、React Hooks 1. useState:这是最基础的Hook,允许函数组件拥有自己的状态。通过调用useState,我们可以添加一个状态变量,并提供一个初始值。每当状态改变时,React会自动重新渲染组件。 ```jsx import React, { useState } from 'react'; function Example() { const [count, setCount] = useState(0); return ( <div> <p>You clicked {count} times</p> <button onClick={() => setCount(count + 1)}> Click me </button> </div> ); } ``` 2. useEffect:用于在函数组件中处理副作用,如订阅、手动更改DOM、定时器等。它有清除功能,确保在组件卸载后清理副作用。 ```jsx import React, { useState, useEffect } from 'react'; function Example() { const [count, setCount] = useState(0); useEffect(() => { // 在此执行副作用,例如订阅或计时器 document.title = `You clicked ${count} times`; // 清除函数,当组件卸载或count变化时执行 return () => { document.title = 'Hello, world!'; }; }, [count]); // 仅当count变化时才重新运行effect return ( <div> <p>You clicked {count} times</p> <button onClick={() => setCount(count + 1)}> Click me </button> </div> ); } ``` 二、自定义React组件 自定义组件是React的核心,它们可以封装可重用的代码,提高代码复用性和组织性。组件通常由纯函数或类构成,遵循以下原则: 1. 单一职责:每个组件只负责一个特定的视觉单元或逻辑单元。 2. 受控组件与非受控组件:受控组件的表单元素值由React控制,而非受控组件则直接监听DOM事件来获取值。 3. Props:组件可以通过props接收外部数据,这些数据不能被组件内部修改,保持了组件的无状态性。 4. State:组件的状态可以被改变,导致组件重新渲染。当使用useState或useReducer Hook时,可以在函数组件中管理状态。 三、React Hooks最佳实践 1. 避免在条件语句或循环中使用 Hooks。这可能导致意外的副作用或不正确的渲染。 2. 使用useCallback优化性能,当函数作为props传递给子组件时,避免不必要的重新渲染。 3. 使用useMemo来缓存计算结果,减少不必要的计算。 4. 适当的组件拆分,保持组件小而专注,提高可读性和可测试性。 在"21-React-Custom"项目中,你可能会学习如何利用React Hooks和自定义组件构建复杂的React应用程序。这个项目可能涵盖了状态管理、生命周期方法的替代、性能优化以及最佳实践等方面。通过深入理解和实践这些概念,你将能够更高效地开发React应用。
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