JSFiddle - React, Tailwind, and code Playground

HTML

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

JavaScript

window.onload = function () {
    var countms = 0;
    var counterms;
    var id_label_ms = document.getElementById("count_label_ms");
    var cronometro = {};
    var ativo = false;

    cronometro.start = function () {
        if (ativo) return;
        ativo = true;
        counterms = setInterval(function () {
            countms = countms + 1;
            id_label_ms.innerHTML = countms / 100 + " s";
        }, 10);
    };

    cronometro.stop = function () {
        clearInterval(counterms);
        ativo = false;
    };

    cronometro.reset = function () {
        cronometro.stop();
        ativo = false;
        id_label_ms.innerHTML = countms = 0;
    };

    ['start', 'stop', 'reset'].forEach(function (tipo) {
        var input = document.querySelector('input[name="' + tipo + '"]');
        input.addEventListener('click', cronometro[tipo]);
    });
};