React.js中JSX的原理与关键实现

npm init -y

npm install webpack webpack-cli -D

npm install babel-loader @babel/core @babel/preset-env -D

npm install @babel/plugin-transform-react-jsx -D

module.exports={
  entry:{
    main:'./main.js'
  },
  module:{
    rules:[
      {
        test:/\.js$/,
        use:{
          loader:'babel-loader',
          options:{
            presets:['@babel/preset-env'],
            plugins:[['@babel/plugin-transform-react-jsx',{pragma:'createElement'}]] // 自定义设置pragma参数，我也可以设置为我的名字：maomin
          }
        }
      }
    ]
  },
  mode:'development',
  optimization:{
    minimize: false
  }
}

// 封装创建Dom节点
class ElementWrapper {
  constructor(type) {
    this.root = document.createElement(type);
  }
  setAttibute(name, value) {
    this.root.setAttibute(name, value);
  }
  appendChild(component) {
    this.root.appendChild(component.root);
  }
}
// 封装插入文本节点
class TextWrapper {
  constructor(content) {
    this.root = document.createTextNode(content);
  }
}
// 组件
export class Component {
  constructor() {
    this.props = Object.create(null); // 创建一个原型为null的空对象
    this.children = [];
    this._root = null;
  }
  setAttribute(name, value) {
    this.props[name] = value;
  }
  appendChild(component) {
    this.children.push(component);
  }
  get root() { // 取值
    if (!this._root) {
      this._root = this.render().root;
    }
    return this._root;
  }
}
// 创建节点，createElement对照 webapck.config.js 中pragma参数。
export function createElement(type, attributes, ...children) {
  let e;
  if (typeof type === "string") {
    e = new ElementWrapper(type);
  } else {
    e = new type();
  }
  for (let p in attributes) { // 循环属性
    e.setAttribute(p, attributes[p]);
  }
  let insertChildren = (children) => {
    for (let child of children) {
      if (typeof child === "string") {
        child = new TextWrapper(child);
      }
      if (typeof child === "object" && child instanceof Array) {
        insertChildren(child); // 递归
      } else {
        e.appendChild(child);
      }
    }
  };
  insertChildren(children);
  return e;
}
// 添加到Dom中
export function render(component, parentElement) {
  parentElement.appendChild(component.root);
}

import {createElement,Component,render} from './reactJsx.js'
class MyComponent extends Component {
  render(){
    return <div>
      <h1>maomin</h1>
      {this.children}
    </div>
  }
}
render(<MyComponent id="name" class="age">
  <div>xqm</div>
  <div>my girlfriend</div>
</MyComponent>,document.body)

npx webpack