checked的选中与取消

<div>    <label for="first"><input id="first" type="checkbox" name="name" value="first"/>first</label>    <label for="second"><input id="second" type="checkbox"  name="name"  value="second"/>second</label>    <label for="third"><input id="third" type="checkbox" name="name"  value="third"/>third</label>    <label for="all"><input id="all" type="checkbox" name="nameAll"  value="all"/>all</label></div></body><script src="https://cdn.bootcss.com/jquery/2.1.1/jquery.min.js"></script><script>    $("input[name='name']").change(function(){        console.log($("input[name='name']:checked").length);        $("input[name='nameAll']").prop("checked","checked")        if($("input[name='name']:checked").length == 0){            $("#all").removeAttr("checked");        }    })</script>