var btn = document.getElementById("btn");btn.onclick = function(event) {var e = EventUtil.getEvent(event);EventUtil.stopPropagation(e); //1、2alert("2");};document.body.addEventListener("click",function(event) {var e = EventUtil.getEvent(event);// EventUtil.stopPropagation(e); //1alert("1");},true);document.body.onclick = function(event) {var e = EventUtil.getEvent(event);// EventUtil.stopPropagation(e); //1、2、3alert("3");};

              <form><input type="text" name="username" value="21" id="adom"><input type="text" οnclick="alert(adom.value)"> <!--21--></form>

<script>var EventUtil = {//事件处理addHandler: function(element, type, handler) {if(element.addEventListener) {element.addEventListener(type, handler, false);} else if(element.attachEvent) {//ie9之前的浏览器的事件监听方式，和上面的方式不一样//attachEvent中的事件类型前有一个onelement.attachEvent("on"+type,handler);} else {element["on"+type] = handler;}},//ie8即更早版本只支持事件冒泡，ie中使用attachEvent//事件处理程序会在全局作用域中运行，所以回调函数中的this等于window，//而不是当前点击的元素getEvent: function(event) {return event ? event : window.event;},//获取目标对象，即当前被点击的元素IE中用event.srcElement获取getTarget: function(event) {return event.target || event.srcElement;},preventDefault: function(event) {if(event.preventDefault) {event.preventDefault();} else {//IEevent.returnValue = false;}},removeHandler: function(element, type, handler) {if(element.removeHandler) {element.removeListener(type, handler, false);} else if(element.detachEvent) {element.detachEvent("on"+type,handler);} else {element["on"+type] = null;}},stopPropagation: function(event) {if(event.stopPropagation) {event.stopPropagation();} else {//IEevent.cancelBubble = true;}}};var btn = document.getElementById("btn");EventUtil.addHandler(btn,"click",function(event) {var e = EventUtil.getEvent(event);
//              alert("hello");});</script>