采用dom实现复选框全选、取消效果

<form action="">
    爱好：<br/>
    <input type="checkbox" id="all">全选<br/>
    <input type="checkbox" name="hobby" value="唱歌">唱歌
    <input type="checkbox" name="hobby" value="跳舞">跳舞
    <input type="checkbox" name="hobby" value="学习">学习
    <input type="checkbox" name="hobby" value="玩耍">玩耍<br/>
    <button id="choice" value="选择">选择</button>
</form>

<script> window.onload = function(){ document.getElementById("all").addEventListener("click",function(){ var a = document.getElementById("all"); var b = document.getElementsByName("hobby"); for(var i=0;i< b.length;i++) { b[i].checked = a.checked; } },false) } </script>