初探babel的转码

写一段基本的class 类

class App extends Component{
constructor(props){
    super(props)
      this.click=this.click.bind(this)
    }
  render(){
  return ([
  <div>nana</div>,
    <h2>mama</h2>
  ])}

}

看看被babel转换成

"use strict";


var _createClass = function () { function defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if ("value" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } } return function (Constructor, protoProps, staticProps) { if (protoProps) defineProperties(Constructor.prototype, protoProps); if (staticProps) defineProperties(Constructor, staticProps); return Constructor; }; }();


function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }


function _possibleConstructorReturn(self, call) { if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return call && (typeof call === "object" || typeof call === "function") ? call : self; }


function _inherits(subClass, superClass) { if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } }); if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass; }


var App = function (_Component) {
  _inherits(App, _Component);


  function App(props) {
    _classCallCheck(this, App);


    var _this = _possibleConstructorReturn(this, (App.__proto__ || Object.getPrototypeOf(App)).call(this, props));


    _this.click = _this.click.bind(_this);
    return _this;
  }


  _createClass(App, [{
    key: "render",
    value: function render() {
      return [React.createElement(
        "div",
        null,
        "nana"
      ), React.createElement(
        "h2",
        null,
        "mama"
      )];
    }
  }]);


  return App;

}(Component);

默认全局严格模式

核心是通过es5的object.defineProperties()方法和IIFE: Immediately Invoked Function Expression，意为立即调用的函数表达式，也就是说，声明函数的同时立即调用这个函数。

es5的单例模式 输出模块