timer.js

class Timer {
    constructor(durationInput, startButton, pauseButton, callbacks) {

        this.durationInput = durationInput;
        this.startButton = startButton;
        this.pauseButton = pauseButton;
        if(callbacks){
            this.onStart = callbacks.onStart;
            this.onTick = callbacks.onTick;
            this.onComplete = callbacks.onComplete;
        }
        this.startButton.addEventListener('click', this.start);
        this.pauseButton.addEventListener('click', this.pause);
    }

    start = () => {
        if(this.onStart){
            this.onStart(this.timeRemaing)
        }
        this.tick();
        this.interval = setInterval(this.tick, 20);
    };

    tick = () => {
        if (this.timeRemaing <= 0) {
            this.pause();
            if(this.onComplete){
                this.onComplete()
            }
        } else {
            this.timeRemaing = this.timeRemaing - .02;
            if(this.onTick){
                this.onTick(this.timeRemaing )
            }
        }

    };

    pause = () => {
        clearInterval(this.interval)
    };

    get timeRemaing() {
        return parseFloat(this.durationInput.value)
    }

    set timeRemaing(time) {
        this.durationInput.value = time.toFixed(2)
    }



}