Stopwatch

function stopwatch() {
     let seconds = 0, minutes = 0, t;

     let time = document.getElementById('time');
     let startbtn = document.getElementById('startBtn');
     let stopbtn = document.getElementById('stopBtn');

     startbtn.addEventListener("click", function(){
        t = setInterval(add, 1000);
        stopbtn.disabled = false;
        startbtn.disabled = true;

    });

     stopbtn.addEventListener("click", function(){
        clearInterval(t);
        seconds = "00";
        minutes = "00";
        time.textContent = `${minutes}:${seconds}`;
        stopbtn.disabled = true;
        startbtn.disabled = false;
      });

    function add() {
        seconds++;
        if(seconds<10){
            seconds=`0` + seconds;
        }

        if (seconds >= 60) {
            seconds = `0` + 0;
            minutes++;
            if(minutes<10){
               minutes=`0` + minutes;
            }
        }
        if(minutes===0){
            minutes=`0` + minutes;
         }
        time.textContent = `${minutes}:${seconds}`;

    }

}