JSFiddle - React, Tailwind, and code Playground

HTML

<p id='txt'>

</p>

JavaScript

var target = 1500000; // 25 mins
var current = 0; // 0 secs
function countdown() {
    current += 1000;
    var diff = target-current;           // calculates the 25 minutes
    var min = Math.floor(diff/1000/60);  //gets mins
    var sec = (diff/1000) % 60;          // gets secs

    document.getElementById("txt").innerHTML = min + ":" + sec;
    if (diff > 0)
       	setTimeout(countdown, 1000);

}

countdown();