Jquery倒计时

<input type="button" value="查询" id="btn" onclick="disableBtn();"/>    <script type="text/javascript">    var waitTime = 60;    function disableBtn() {        $("#btn").attr("disabled", true);//禁用按钮        $("#btn").attr("value", "倒计时(" + waitTime + ")");//按钮文字加上倒计时的秒        waitTime--;//变量每秒减一        if (waitTime >= 0) {                setTimeout(function () {                disableBtn();//如果waitTime变量大于0则调用当前方法，每秒执行一次            }, 1000);        } else {            waitTime = 60;//重置            $("#btn").removeAttr("disabled", true);//启用按钮            $("#btn").attr("value", "查询");        }    }    </script>