JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8" />
    <title> timer </title>
</head>
<body>
    <input type="text" id="theField" value="1">
    <button onclick="start_timer();"> start timer </button>
    <button onclick="stop_timer();"> stop timer </button> 
</body>
</html>

JavaScript

function start_timer(){
    document.getElementById('theField').value++;
    timerVariable = setTimeout('start_timer()',1000);
    console.log('set timeout return value: ' + timerVariable);
}

function stop_timer(){
    clearTimeout(timerVariable);
    console.log('clearing timeout: ' + timerVariable);
}