js原生 阻止冒泡事件的方法

function stopPropagation(e) {  
    e = e || window.event;  
    if(e.stopPropagation) { //W3C阻止冒泡方法  
        e.stopPropagation();  
    } else {  
        e.cancelBubble = true; //IE阻止冒泡方法  
    }  
} 

box2.onmouseover=function(e){
          console.log(22);
         stopPropagation(e);
 }