<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style type="text/css">
</style>
</head>
<body>
<input type="checkbox" id="checkall" onclick="checkAll()"><lable for="checkall">全选</lable>
<hr>
<input type="checkbox" name="item[]">选项1<br>
<input type="checkbox" name="item[]">选项2<br>
<input type="checkbox" name="item[]">选项3<br>
<input type="checkbox" name="item[]">选项4<br>
<input type="checkbox" name="item[]">选项5<br>
<input type="checkbox" name="item[]">选项6<br>
<input type="checkbox" name="item[]">选项7<br>
<input type="checkbox" name="item[]">选项8<br>
<input type="checkbox" name="item[]">选项9<br>
<input type="checkbox" name="item[]">选项10<br>
<br>
<p>分别使用for循环，while循环,do while循环做了全选的案例,都可以实现效果，那么这三种循环语句是否可以互相替代通用呢？</p>
<script type="text/javascript">
/* function checkAll(){
var checkall , item;
checkall = document.getElementById('checkall');
item = document.getElementsByName('item[]');
for(var i = 0; i<item.length; i++){
if(checkall.checked){
item[i].checked = true;
}else{
item[i].checked = false;
}
}
} */
/* function checkAll(){
var checkall , item;
checkall = document.getElementById('checkall');
item = document.getElementsByName('item[]');
var i=0;
while(i<=item.length){
if(checkall.checked){
item[i].checked = true;
}else{
item[i].checked = false;
}
i++;
}
} */
function checkAll(){
var checkall , item;
checkall = document.getElementById('checkall');
item = document.getElementsByName('item[]');
var i=0;
do{
if(checkall.checked){
item[i].checked = true;
}else{
item[i].checked = false;
}
i++
}while(i<=item.length);
}
</script>
</body>
</html>
