原生js阻止冒泡，兼容写法

js:

var $item = document.getElementById('item');
 $item.onclick = function (e) {//阻止冒泡
            if (e) {
              e.stopPropagation();
              e.preventDefault();
            } else {
              window.event.returnValue = false;
              window.event.cancelBubble = true;
            }
          }

html:

<div id="item">点击</div>