JSFiddle - React, Tailwind, and code Playground

HTML

<h3>test</h3>

JavaScript

let h=10;
let m=0;
let s=0;

timerDisplay();

function timerDisplay() {
  let time = h * 360 + m * 6 + s;
  neverGiveYouUp();
  setInterval(() => {
    neverGiveYouUp();
  }, 1000)
}

function neverGiveYouUp() {
  document.querySelector('h3').innerHTML = `${h}:${m}:${s}`

  if(h == 0 && m == 0 && s == 0) {
    document.querySelector('h3').style.display = 'none'
  }
  if(m == 0 && s == 0) {
    if(h > 0) {
      m = 59
      h--
    }
  }
  if(s == 0) {
    s = 59
    m--
  } 
  else {s--}
}