function getTimeRemaining(endtime){
    const total = Date.parse(endtime) - Date.parse(new Date());
    const seconds = Math.floor( (total/1000) % 60 );
    const minutes = Math.floor( (total/1000/60) % 60 );
    const hours = Math.floor( (total/(1000*60*60)) % 24 );
    const days = Math.floor( total/(1000*60*60*24) );

    return {
        total,
        days,
        hours,
        minutes,
        seconds
    };
}

function initializeClock(id, endtime) {
    const clock = document.getElementById(id);

    const daysSpan = clock.querySelector('.days');
    const hoursSpan = clock.querySelector('.hours');
    const minutesSpan = clock.querySelector('.minutes');
    const secondsSpan = clock.querySelector('.seconds');

    function updateClock() {
        const t = getTimeRemaining(endtime);

        if (t.days < 0) {
            clearInterval(timeinterval);
            $('#clock-card').hide();
        }

        daysSpan.innerHTML = t.days;
        hoursSpan.innerHTML = ('0' + t.hours).slice(-2);
        minutesSpan.innerHTML = ('0' + t.minutes).slice(-2);
        secondsSpan.innerHTML = ('0' + t.seconds).slice(-2);

        if (t.total <= 0) {
            clearInterval(timeinterval);
        }
    }

    updateClock(); // run function once at first to avoid delay
    var timeinterval = setInterval(updateClock, 1000);
}

initializeClock('clockdiv', deadline);
$('#trip-name').text(tripName);