js事件相关

 //添加事件兼容
  function addEvent(obj, type, fn) {
	if (obj.addEventListener) {
		obj.addEventListener(type, fn);
	} else if (obj.attachEvent) {
		obj.attachEvent('on' + type, fn);
	}
  }

 //移除事件
function removeEvent(obj, type, fn) {
	if (obj.removeEventListener) {
		obj.removeEventListener(type, fn);
	} else if (obj.detachEvent) {
		obj.detachEvent('on' + type, fn);
	}
  }

  //获取relatedTarget
  function getTarget(evt) {
	var e = evt || window.event;
	if (e.srcElement) {
		if (e.type == 'mouseover') {
			return e.fromElement;
		} else if (e.type == 'mouseout') {
			return e.toElement;
		}
	} else if (e.relatedTarget) {
		return e.relatedTarget;
	}
  }

 //阻止事件冒泡
function stopBubble(e) { 
	var e = evt || window.event;
	if (e.stopPropagation ) {
		e.stopPropagation(); 
	}else {
		e.cancelBubble = true; 
	}
}

 //阻止默认事件
  function preDef(evt) {
	var e = evt || window.event;
	if (e.preventDefault) {
		e.preventDefault();
	} else {
		e.returnValue = false;
	}
 }


//获取wheelDelta
 function getWD(evt) {
	var e = evt || window.event;
	if (e.wheelDelta) {
		return e.wheelDelta;
	} else if (e.detail) {
		return -evt.detail * 30;
	}
}