jquery ------ 分鐘倒計時

<span class="cuclock">15:00</span>

        
        /**
         * 倒計時
         * cutTime 是 min * sec 
         * 例：倒計時10分鐘 var cutTime = 10 * 60
         **/

        let cutTime = 15 * 60;
        let summer = setInterval(counClock, 1000);

        function counClock() {
            let min = '';
            let sec = '';

            if (cutTime > 0) {
                min = Math.floor(cutTime / 60);
                sec = Math.floor(cutTime % 60);
                if (sec < 10) {
                    sec = '0' + sec;
                };
                cutTime--;
            } else {
                $(".Mask").hide();
                clearInterval(summer);
            }

            $(".cuclock").text(min + ':' + sec);
        }