点击获取短信验证码 倒计时

<input type="button" class="btn_get_code" value="获取短信验证码" id="btn_get_phonecode" onclick="send_code()">

//倒计时
  $(function () {
            $('#btn_get_phonecode').click(function () {
                var count = 60;
                var countdown = setInterval(CountDown, 1000);
                function CountDown() {
                    $("#btn_get_phonecode").attr("disabled", true);
                    $("#btn_get_phonecode").val(count + " 秒后从新获取!");
                    if (count == 0) {
                        $("#btn_get_phonecode").val("从新获取验证码").removeAttr("disabled");
                        clearInterval(countdown);
                    }
                    count--;
     $('.phonecode_tips').show(); 
                }
            })
        });