JSFiddle - React, Tailwind, and code Playground

by grammar

HTML

<div class="timer-display-value"></div>

JavaScript

const timer = {
   timePassed : 0,
   countStart : Date.now(),
   display : document.querySelector(".timer-display-value"),
   updateTimer : function() {
    let delta = Date.now() - this.countStart;
    this.timePassed = Math.floor(delta / 1000);
    this.display.textContent = this.timePassed;
   },
   startTiming : function() {
     this.interval = setInterval(() => { 
        this.updateTimer();
     }, 500);
   },
   start : function() {
     this.countStart = Date.now();
     this.startTiming();
   },
   stop : function() {
     clearInterval(this.interval);
   }
};

timer.start();