<html>
<head>
<title>全选和取消全选</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<script language="javascript">
function checkAllorcancelAll(){
//思路：1.获取checkbox的选中状态；1.1获取checkbox元素
var chkElt = document.getElementById("chkElt");
//1.2获取选中状态
var checked = chkElt.checked;
//2.若checked=true，选中所有复选框；
//2.1获取所有复选框
var allInterests = document.getElementsByName("interest");
//2.2遍历取出每个复选框对象
var mySpan = document.getElementById("mySpan");
if(checked){
//全选,设置复选框的选中状态
for(var i=0;i<allInterests.length;i++){
allInterests[i].checked = true;
}
mySpan.innerHTML="取消全选";
}else{
//取消全选
checked=false;
for(var i=0;i<allInterests.length;i++){
allInterests[i].checked = false;
}
mySpan.innerHTML="全选";
}
}
</script>
</head>
<body>
<input type = "checkbox" id="chkElt" onclick="checkAllorcancelAll()">
<span id="mySpan">全选</span><br>
运动<input type = "checkbox" name="interest" value="sport" /><br>
音乐<input type = "checkbox" name="interest" value="music" /><br>
美食<input type = "checkbox" name="interest" value="food" /><br>
睡觉<input type = "checkbox" name="interest" value="sleep" /><br>
跳舞<input type = "checkbox" name="interest" value="dance" /><br>
</body>
</html>
</html>
原文：http://www.cnblogs.com/wangqiang4518/p/5730998.html