React源码--constructor

import React from './react-dev/react';
import { render } from './react-dev/react-dom';
class App extends React.Component {
  constructor(props) {
    super(props);
    this.state = {count: 0};
    this.handleClick = this.handleClick.bind(this);
  }

  handleClick(event) {
    console.log('hello');
    console.log('event', event);
    this.setState((state) => {
        console.log('sasa');
        return {count: state.count + 1};
    });
  }

  render() {
    return [
        <button key="1" onClick={this.handleClick}>Update counter</button>,
        <span key="2">{this.state.count}</span>
    ]
  }
}

render(<App />, document.getElementById('app'));

./node_modules/.bin/babel src/index.jsx

function App(propss) {
    var _this;

    _classCallCheck(this, App);
    // 注意这行
    _this = _super.call(this, propss);
    _this.state = {
      count: 0
    };
    _this.handleClick = _this.handleClick.bind(_assertThisInitialized(_this));
    return _this;
}

function App(props) {
    var _this;

    _classCallCheck(this, App);

    // super(props);
    _this.state = {
        count: 0
    };
    _this.handleClick = _this.handleClick.bind(_assertThisInitialized(_this));
    return _possibleConstructorReturn(_this);
}