javascript 거품 발생 및 기본 이벤트 사용 에 대한 자세 한 설명

<script type="text/javascript">
 window.onload=function(){
 var a=document.getElementById("a");
 var b=document.getElementById("b");
 var c=document.getElementById("c");
 var c=document.getElementById("d");

     a.onclick=function(e){
         this.style.background="#000";    
         };

     b.onclick=function(e){
             this.style.background="#ccc";
             //      
             window.event.cancelBubble = true;//IE8  
             e.stopPropagation();
         };

     d.onmousedown=function(e){
         //      ，   chrome          
         window.event.returnValue = false;
         e.preventDefault();
     }
 }

 

 </script>

Html   
 <div id="a" style="width:300px;height:300px;background:red;overflow:hidden;">
     <div id="b" style="width:200px;height:200px;background:green;margin:50px 0 0 50px;overflow:hidden;">
         <div id="c" style="width:100px;height:100px;background:yellow;margin:50px 0 0 50px;overflow:hidden;">
             <img src="240x240.jpg" width="50" height="50" id="d" />
         </div>
     </div>
 </div>

<script type="text/javascript">
window.onload=function(){
    document.getElementById("test").addEventListener('click',function(e){
        alert('aaaa')
    },false);

    document.getElementById("test1").addEventListener('click',function(e){
        alert('bbb')
        e.stopPropagation();
    },false)
}
</script>

<style type="text/css">
#test1{width:100px;height:100px;background:#ff0}
#test2{width:100px;height:100px;background:#ff0}
</style>
<div id="test" style="width:100px;height:100px;background:#f60;padding:20px;">
    <div id="test1"></div>
</div>