全选框制作（作业）
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>全选</title>
<style>
body{
padding: 0;
margin:0;
}
.box{
height: 200px;
width: 100px;
border: 1px solid #ccc;
margin:20px auto;
border-radius: 10px;
}
.box p{
margin: 0px;
padding: 4px;
}
.box p:first-of-type{
border-bottom: 1px solid #ccc;
}
</style>
</head>
<body>
<div>
<p>
<label><input type="checkbox" id="checkall" onclick="checkAll()">全选</label>
</p>
<p><label><input type="checkbox" name="item[]" >选项1</label></p>
<p><label><input type="checkbox" name="item[]">选项2</label></p>
<p><label><input type="checkbox" name="item[]">选项3</label></p>
<p><label><input type="checkbox" name="item[]">选项4</label></p>
<p><label><input type="checkbox" name="item[]">选项5</label></p>
<p><label><input type="checkbox" name="item[]">选项6</label></p>
</div>
<script>
function checkAll(){
var checkall = document.getElementById('checkall'); //获取全选框
var item = document.getElementsByName('item[]');//获取选项框
for(var i=0;i<item.length;i++){
if (checkall.checked) {
item[i].checked = true;
}else{
item[i].checked = false;
}
}
}
</script>
</body>
</html>