复选框的全选和取消

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>复选框的全选和取消</title>
<script type="text/javascript">
function selectAll(ckname){
var ck=document.getElementsByName(ckname);
for(i=0;i<ck.length;i++)
ck[i].checked=true;
}
function unselectAll(ckname){
var ck=document.getElementsByName(ckname);
for(i=0;i<ck.length;i++)
ck[i].checked=false;
}
</script>
</head>
<body>
<form>
<input type="button" value="全选" onclick="selectAll('interest')">
<input type="button" value="取消选择" onclick="unselectAll('interest')">
<input type="checkbox" name="interest" value="study"/>学习
<input type="checkbox" name="interest" value="read"/>阅读
<input type="checkbox" name="interest" value="sport"/>运动
<input type="checkbox" name="interest" value="travel"/>旅行
<input type="checkbox" name="interest" value="draw"/>绘画
<input type="checkbox" name="interest" value="music"/>音乐

</form>
</body>
</html>