index.html 檔案代碼：
<!DOCTYPE>
<html>
<head >
<title>DOM</title>
<meta charset="utf-8">
<script type="text/javascript" src="myjs.js"></script>
<style>
.blue{
background-color: blue;
width: 200px;
height: 100px;
border: 1px solid black;
}
.red{
background-color: red;
width: 200px;
height: 100px;
border: 1px solid black;
}
</style>
</head>
<body>
<div id="box" class="red">box
</div>
</body>
</html>
myjs.js檔案代碼：
function toBlue(){
this.className = 'blue';
this.removeEventListener('click',toBlue,false);
this.addEventListener('click',toRed,false);
}
function toRed(){
this.className = 'red';
this.removeEventListener('click',toRed,false);
this.addEventListener('click',toBlue,false);
}
window.addEventListener('load',function(){
var box = document.getElementById('box');
box.addEventListener('click',toBlue,false);
},false);
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