事件流测试

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JS Bin</title>
  <style>
    #xxx {
  
  width: 200px;
  height: 200px;
  padding: 10px;
}
div {
  box-sizing: border-box;
  padding: 10px;
  height: 100%;
  width: 100%;
  border: 1px solid black;
}
  </style>
</head>
<body>
<div id='xxx'>
  <div id='xx'>
    <div id='x'></div>
  </div>
</div>
  <script>
    var xxx = document.querySelector('#xxx')
xxx.addEventListener('click',function(){
  alert(3)
},false)
var xx = document.querySelector('#xx')
xx.addEventListener('click',function(){
  alert(2)
})
var x = document.querySelector('#x')
x.addEventListener('click',function(e){
  alert(1)
  e.stopPropagation()
})
  </script>
</body>
</html>

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