React进阶笔记

1. 事件监听

React中使用onClick类似的写法来监听事件，注意this绑定问题 react里严格遵循单项数据流，没有数据双向绑定，

所以输入框要设置value和onChange 

handleChange(e){ this.setState({ name:e.target.value }) }
 <input type="text" value={this.state.name} onChange={(e)=>this.handleChange(e)} />

2.  PureComponent Vs Component  https://www.jianshu.com/p/c41bbbc20e65

3.  React.memo

React v16.6.0 之后的版本，可以使用 React.memo 让函数式的组件也有PureComponent的功能 

4. HOC（Higher-Order Components） 高阶组件

高阶组件也是一个组件，但是他返回另外一个组件，产生新的组件可以对属性进行包装，甚至重写部分生命周期 

const withKaikeba = (Component) => { const NewComponent = (props) => { return <Component {...props} name="开课吧高阶组件" />; };return NewComponent; };

上面withKaikeba组件，其实就是代理了Component，只是多传递了一个name参数 

5. 高阶组件最巧妙的一点，是可以链式调用。

import React, {Component} from 'react'
import {Button} from 'antd'
const withKaikeba = (Component) => {
    const NewComponent = (props) => {
        return <Component { ...props } name = "开课吧高阶组件" / > ;
    };
    return NewComponent;
};
const withLog = Component => {
    class NewComponent extends React.Component {
        render() {
            return <Component { ...this.props }  />;
        }
        componentDidMount() {
            console.log('didMount', this.props)
        }
    } return NewComponent
}
class App extends Component {
    render() {
        return (
            <div className="App">
                <h2>hi,{this.props.name}</h2 >
                < Button type="primary" > Button < /Button>
                </div >
             )
   }
   }
export default withKaikeba(withLog(App))

6. 高阶组件装饰器写法

npm install --save-dev babel-plugin-transform-decorators-legacy

const { injectBabelPlugin } = require("react-app-rewired");
module.exports = function override(config) {
  config = injectBabelPlugin(
    [
      "import",
      {
        libraryName: "antd",
        libraryDirectory: "es",
        style: "css"
      }
    ],
    config
  );
  config = injectBabelPlugin(
    [
      "@babel/plugin-proposal-decorators",
      {
        legacy: true
      }
    ],
    config
  );
  return config;
};

使用装饰器

import React, { Component } from 'react'
import { Button } from 'antd'
const withKaikeba = (Component) => {
    const NewComponent = (props) => {
        return <Component { ...props } name="开课吧高阶组件" />;
    };
    return NewComponent;
};
const withLog = Component => {
    class NewComponent extends React.Component {
        render() {
            return <Component {  ...this.props } />;
        }
        componentDidMount() {
            console.log(Component.name, 'didMount', this.props)
        }
    } return NewComponent
}
@withKaikeba 
@withLog 
class App extends Component {
    render() {
        return (
            <div className="App">
                <h2>hi,{this.props.name}</h2 >
                < Button type="primary" > Button < /Button> 
                </div > 
            )
        }
}
export default App

7.  按需加载

1.安装react-app-rewired取代react-scripts，可以扩展webpack的配置 ，类似vue.confifig.js

npm install react-app-rewired@2.0.2-next.0 babel-plugin-import --save

2.根目录创建config-overrides.js 文件

const {injectBabelPlugin} = require('react-app-rewired');

module.exports = function override(config, env) {

    config = injectBabelPlugin(
        ['import', {libraryName: 'antd', libraryDirectory: 'es', style: 'css'}],
        config
    );

    config = injectBabelPlugin([
        "@babel/plugin-proposal-decorators",
        {
            "legacy": true
        }
    ], config);

    return config;

};

3.把package.json的react-script 替换为 react-app-rewired

  "scripts": {
    "start": "react-app-rewired start",
    "build": "react-app-rewired build && mkdir ./build/views/ && mv ./build/index.html ./build/views/",
    "test": "react-app-rewired test --env=jsdom"
  }

 8.