JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <span id="timer_out">0</span>
    </br>
    <input type="button" value="Start" onclick="start()"/>
    <input type="button" value="Stop" onclick="stop()"/>
    <input type="button" value="Reset" onclick="reset()"/>
</div>

JavaScript

var i, timer, divide;

window.onload = function() {
	i = 0;
	divide = 100;
}

function start() {
    if (!timer) {
        timer = setInterval("increment()", (1000 / divide)); 
    }
}

function increment() {
    i++;
    document.getElementById("timer_out").innerHTML = (i / divide);
}

function stop() {
    clearInterval(timer);
    timer = null;
}

function reset() {
    stop();
    i = 0;
    document.getElementById("timer_out").innerHTML = (i / divide);
}