A Minimal Pure Javascript Stopwatch

A simple lightweight Javascript stopwatch which allows you to count up from zero with start, pause, resume and stop controls. Created by cathydutton.

Basic Usage:

Create the Html for a stopwatch.

<p><span id="seconds">00</span>:<span id="tens">00</span></p>

Create some controls for the stopwatch.

<button id="button-start">Start</button>
<button id="button-stop">Stop</button>
<button id="button-reset">Reset</button>

The Javascript to enable the stopwatch.

window.onload = function () {
  
  var seconds = 00; 
  var tens = 00; 
  var appendTens = document.getElementById("tens")
  var appendSeconds = document.getElementById("seconds")
  var buttonStart = document.getElementById('button-start');
  var buttonStop = document.getElementById('button-stop');
  var buttonReset = document.getElementById('button-reset');
  var Interval ;
  buttonStart.onclick = function() {
    
     clearInterval(Interval);
     Interval = setInterval(startTimer, 10);
  }
  
    buttonStop.onclick = function() {
       clearInterval(Interval);
  }
  
  buttonReset.onclick = function() {
     clearInterval(Interval);
    tens = "00";
  	seconds = "00";
    appendTens.innerHTML = tens;
  	appendSeconds.innerHTML = seconds;
  }
  
   
  
  function startTimer () {
    tens++; 
    
    if(tens < 9){
      appendTens.innerHTML = "0" + tens;
    }
    
    if (tens > 9){
      appendTens.innerHTML = tens;
      
    } 
    
    if (tens > 99) {
      console.log("seconds");
      seconds++;
      appendSeconds.innerHTML = "0" + seconds;
      tens = 0;
      appendTens.innerHTML = "0" + 0;
    }
    
    if (seconds > 9){
      appendSeconds.innerHTML = seconds;
    }
  
  }
  
}