function timer() {
    let count = 0;
    let time;
    let ckliked = true;
    //start
    $('#start-timer').click(function () {

        if (ckliked) {
            count=0;
            counter();

            time = setInterval(counter, 1000);
            ckliked = false;
        }
    });
    //stop
    $('#stop-timer').click(function () {
        ckliked = true;
        clearInterval(time);
    });

    function counter() {

        let seconds = count % 60;
        let minutes = ((count - count % 60) / 60) % 60;
        let hours = Math.floor(((count - seconds) / 60) / 60);
        $('#seconds').text(('0' + `${seconds}`).slice(-2));
        $('#minutes').text(('0' + `${minutes}`).slice(-2));
        $('#hours').text(('0' + `${hours}`));
        count++;
    }
}