// KONSTRUKTOR
function intervalTimer(callback, interval) {
    let
        startTime,
        remaining = 0,
        state = 0; //  0 = idle, 1 = running, 2 = paused, 3= resumed

    this.pause = function() {
        if (state != 1) {
            return;
        }

        remaining = interval - (new Date() - startTime);
        window.clearInterval(timerId);
        state = 2;
    };

    this.resume = function() {
        if (state != 2) {
            return;
        }

        state = 3;
        window.setTimout(this.timeoutCallback, remaining);
    };

    this.timeoutCallback = function() {
        if (state != 3) {
            return;
        }

        callback();

        startTime = new Date();
        timerId = window.setInterval(callback, interval);
        state = 1;
    };

    startTime = new Date();
    timerId = window.setInterval(callback, interval);
    state = 1;
}

//NOWY OBJEKT
    let clockInterval = new intervalTimer(function() {
        if (seconds.innerHTML == 0) {
            if (minutes.innerHTML !== "00") {
                minutes.innerHTML -= 1;
                minutes.innerHTML = leadingZeros(minutes.innerHTML);
                seconds.innerHTML = "59";
            }

            else if (minutes.innerHTML == "00") {
                clearInterval(clock);
            }
        }

        else if (seconds.innerHTML !== 0) {
            seconds.innerHTML -= 1;
            seconds.innerHTML = leadingZeros(seconds.innerHTML);
        }
    }, 1000);

// DZIAŁA
    resumePause.addEventListener("click", function() {
        clockInterval.pause();
    })

// NIE DZIAŁA
    resumePause.addEventListener("click", clockInterval.pause());