JSFiddle - React, Tailwind, and code Playground

HTML

<div id="timer"> 
     <span id="minute" class="dis">00</span> : 
     <span id="second" class="dis">00</span> : 
     <span id="milisecond" class="dis">00</span> 
 </div>
 
 <input type="button" value="Start/Stop" id="startStop" />
 <input type="button" value="Reset" id="reset" />

JavaScript

var a = false,
         t = null,
         ms = 0,
         s = 0,
         m = 0,
         dl = 10,
         now = null,
         before = new Date(),
         El = function(id) { return document.getElementById(id);};
     
     function dsp() {
         if(ms++ == 99){
              ms = 0; 
             if(s++ == 59) {
                 s = 0;
                 m++;
             } else s = s;
         } else ms = ms;    
         El('milisecond').innerHTML = ms
         El('second').innerHTML = s < 10 ? '0' + s : s;
         El('minute').innerHTML = m < 10 ? '0' + m : m;
     }
     
     function r() {
         a = true;
         var els = document.getElementsByClassName('dis');
         ms = s = m = 0;
         sw();        
         for(var i in els)  {
             els[i].innerHTML = '00';    
         }
     }
     
     function sw() {
         a ? clearInterval(t) : t = setInterval(dsp, dl);
         a = !a;
     }
     El('startStop').addEventListener('click', sw, true);
     El('reset').addEventListener('click', r, true);