자바스크립트 카운트다운 알람 질문있습니다.

/*시간 카운트다운*/

 

// Set the date we're counting down to

 

var countDownDate = new Date("Jun 21, 2018 17:30:00").getTime();

 

// Update the count down every 1 second

var countdownfunction = setInterval(function() {

 

    // Get todays date and time

    var now = new Date().getTime();

    

    // Find the distance between now an the count down date

    var distance = countDownDate - now;

    

    // Time calculations for days, hours, minutes and seconds

    var days = Math.floor(distance / (1000 * 60 * 60 * 24));

    var hours = Math.floor((distance % (1000 * 60 * 60 * 24)) / (1000 * 60 * 60));

    var minutes = Math.floor((distance % (1000 * 60 * 60)) / (1000 * 60));

    var seconds = Math.floor((distance % (1000 * 60)) / 1000);

    

    // Output the result in an element with id="demo"

    document.getElementById("demo").innerHTML = days + "d " + hours + "h "

    + minutes + "m " + seconds + "s ";

    

    // If the count down is over, write some text 

    if (distance < 0) {

        clearInterval(countdownfunction);

        document.getElementById("demo").innerHTML = "퇴근완료";

    }

}, 1000);