javascript事件模型的驱动方式

Rico中是这样判断的
 initializeEventHandlers: function() {
          if ( typeof document.implementation != "undefined" &&
             document.implementation.hasFeature("HTML",   "1.0") &&
             document.implementation.hasFeature("Events", "2.0") &&
             document.implementation.hasFeature("CSS",    "2.0") ) {
             document.addEventListener("mouseup",   this._mouseUpHandler.bindAsEventListener(this),  false);
             document.addEventListener("mousemove", this._mouseMoveHandler.bindAsEventListener(this), false);
          }
          else {
             document.attachEvent( "onmouseup",   this._mouseUpHandler.bindAsEventListener(this) );
             document.attachEvent( "onmousemove", this._mouseMoveHandler.bindAsEventListener(this) );
          }
       }