javascript带回调函数的异步脚本载入方法实例分析

var Loader = function () { }Loader.prototype = {  require: function (scripts, callback) {    this.loadCount   = 0;    this.totalRequired = scripts.length;    this.callback    = callback;    for (var i = 0; i < scripts.length; i++) {      this.writeScript(scripts[i]);    }  },  loaded: function (evt) {    this.loadCount++;    if (this.loadCount == this.totalRequired && typeof this.callback == 'function') this.callback.call();  },  writeScript: function (src) {    var self = this;    var s = document.createElement('script');    s.type = "text/javascript";    s.async = true;    s.src = src;    s.addEventListener('load', function (e) { self.loaded(e); }, false);    var head = document.getElementsByTagName('head')[0];    head.appendChild(s);  }}

var l = new Loader();l.require([  "example-script-1.js",  "example-script-2.js"],  function() {    // Callback    console.log('All Scripts Loaded');  });