JSFiddle - React, Tailwind, and code Playground

HTML

<label id=count_label_ms></label>
<br>
<p>
    <input type=button value="stop" onclick="stop()" />
    <input type=button value="reset" onclick="reset()" />
    <input type=button value="start" onclick="start()" />
</p>

JavaScript

var countms = 0;
var intervalTxt = null;
function start() {
     var id_label_ms = document.getElementById("count_label_ms");
            if (intervalTxt == null) {
              
                intervalTxt = setInterval(function() {
                countms = countms + 1;
               
                id_label_ms.innerHTML =  countms / 100 + " s";
               }, 1);
            }
}

function stop() {
         if (intervalTxt != null) {
            var id_label_ms = document.getElementById("count_label_ms");
            clearInterval(intervalTxt);
             intervalTxt = null;
            id_label_ms.innerHTML =  countms / 100 + " s";
          }
}

function reset() {
     var id_label_ms = document.getElementById("count_label_ms");
     clearInterval(intervalTxt);
     intervalTxt = null;
     id_label_ms.innerHTML = 0 + " s";
}