跨浏览器dom事件方法

var EventUtil = {
 // 添加事件
  addHandler: function (element, type, handler) {
      if (element.addEventListener) {
          element.addEventListener(type, handler, false);
      } else if (element.attachEvent) {
            element.attachEvent("on" + type, handler);
       } else {
         element["on" + type] = handler;
      }
    },
   // 移除事件
  removeHandler: function (element, type, handler) {
       if (element.removeEventListener) {
           element.removeEventListener(type, handler, false);
       } else if (element.detachEvent) {
            element.detachEvent("on" + type, handler);
       } else {
         element["on" + type] = null;
     }
    }
    // 获取事件对象
    getEvent: function (event) {
     return event ? event : window.event;
 },
   // 获取目标对象
    getTarget: function (event) {
        return event.target || event.srcElement;
 },
   // 阻止默认事件
    preventDefault: function (event) {
       if (event.preventDefault) {
          event.preventDefault();
      } else {
         event.returnValue = false;
       }
    },
   // 阻止（冒泡）事件传播
    stopPropagation: function (event) {
      if (event.stopPropagation) {
         event.stopPropagation();
     } else {
         event.cancelBubble = true;
       }
    },
   // 获取鼠标按键
    getButton: function (event) {
        if (document.implementation.hasFeature("MouseEvents", "2.0")) {
          return event.button;
     } else {
         switch (event.button) {
              case 0:
              case 1:
              case 3:
              case 5:
              case 7:
                  return 0;
                case 2:
              case 6:
                  return 2;
                case 4:
                  return 1;
            }
        }
    }
}