全选，选中与清除效果
这节学习了全选内容
<html>
<head>
<meta charset="UTF-8">
<title>全選</title>
<style>
.box{
width:120px;
height:250px;
border:1px solid #000;
border-radius:5px;
padding:5px 10px;
margin:20px auto;
}
.box div{
border-bottom:1px solid #000;
padding-bottom:10px;
margin-bottom:8px;
}
.box intpu{
margin:8px;
}
</style>
<script type='text/javascript'>
function checkAll(){
var checkall,item;
checkall=document.getElementById('checkall');//獲取全選
item = document.getElementsByName('item[]');//獲取下面勾選框
for (var i=0;i<item.length;i++){
if(checkall.checked){
item[i].checked=true;//當全選被選中時，勾選框選中
}else{
item[i].checked=false;//反之清空
}
}
}
</script>
</head>
<body>
<div class='box'>
<div>
<input type="checkbox"id="checkall"onclick="checkAll()"><label for="checkall">全選</label>
</div>
<input type='checkbox'name='item[]'>選項1<br>
<input type='checkbox'name='item[]'>選項2<br>
<input type='checkbox'name='item[]'>選項3<br>
</div>
</body>
</html>