JSFiddle - React, Tailwind, and code Playground

HTML

<div id="waiting_time"></div>

JavaScript

var isWaiting = false;
var isRunning = false;
var seconds = 10;
var countdownTimer;
var finalCountdown = false;

function GameTimer() {
    var minutes = Math.round((seconds - 30) / 60);
    var remainingSeconds = seconds % 60;
    if (remainingSeconds < 10) {
        remainingSeconds = "0" + remainingSeconds;
    }
    document.getElementById('waiting_time').innerHTML = minutes + ":" + remainingSeconds;
    if (seconds == 0) {
        isRunning = true;
        seconds += 2;
        
        if (finalCountdown) {
            clearInterval(countdownTimer);
        } else {
            finalCountdown = true;
        }

    } else {
        isWaiting = true;
        seconds--;
    }
}
countdownTimer = setInterval(GameTimer, 1000);