04. Stopwatch Lab: DOM Manipulations

function stopwatch() {
    let startButton = document.getElementById('startBtn');
    startButton.addEventListener('click', start);
    let stopButon = document.getElementById('stopBtn');
    stopButon.addEventListener('click', stop);
    let outputBox = document.getElementById('time');
    let timer = null;
    function stop() {
        stopButon.disabled = true;
        startButton.disabled = false;
        clearInterval(timer);
    }
    function start() {
        startButton.disabled = true;
        stopButon.disabled = false;
        let seconds = 0;
        timer = setInterval(tick, 1000);
        outputBox.textContent = '00:00';

        function tick() {
            seconds++;
            let currentMinute = ('0' + Math.floor(seconds / 60)).slice(-2);
            let currentSecond = ('0' + seconds % 60).slice(-2);
            outputBox.textContent = `${currentMinute}:${currentSecond}`;
        }
    }
}