jQuery checkbox 全选、全取消

<script type="text/javascript" language="javascript"> 
    $(function() {
        $("#checkedAll").click(function() {
            if ($(this).attr("checked") == true) { // 全选
                    $("input[@type='checkbox']").each(function() {
                    $(this).attr("checked", true);
                    });
                } else { // 取消全选
                    $("input[@type='checkbox']").each(function() {
                    $(this).attr("checked", false);
                });
            }
        });
    });
     </script>