JSFiddle - React, Tailwind, and code Playground

HTML

<div class="time">Time: <span id="timer">?</span></div>

JavaScript

var hour = 2;
  var minute = 46;
  var second = 45;

  // function to make a counter
  function clockIt() {
    function clockO(digit) {
      if(digit<10) {
        return '0';
      } else {
        return '';
      }
    }

    document.getElementById('timer').textContent = hour + ':' + clockO(minute) + minute + ':' + clockO(second) + second;
    if(second>0) {
      second -= 1;
    } else if(minute>0) {
      minute -= 1;
      second += 59;
    } else if(hour>0) {
      hour -= 1;
      minute += 59;
    }
  }

  // runs the function every seconds
  clockIt();
  setInterval(function (){clockIt()}, 1000);