code: function addEventListener(type, listener, useCapture) {
        if (type === 'DOMContentLoaded') type = 'load';
        var target = this;
        var f = function(e) {
          e._timeStamp = Date.now();
          e._currentTarget = target;
          listener.call(this, e);
          e._currentTarget = null;
        };
        this['_' + type + listener] = f;
        this.attachEvent('on' + type, f);
      }
docs: interface EventTarget