<style style="text/css">
.clock {
  font-size: 4em;
}
</style>
<script>
function clock() {// We create a new Date object and assign it to a variable called "time".
var time = new Date(),
    
    // Access the "getHours" method on the Date object with the dot accessor.
    hours = time.getHours(),
    
    // Access the "getMinutes" method with the dot accessor.
    minutes = time.getMinutes(),
    
    
    seconds = time.getSeconds();

document.querySelectorAll('.clock')[0].innerHTML = harold(hours) + ":" + harold(minutes) + ":" + harold(seconds);
  
  function harold(standIn) {
    if (standIn < 10) {
      standIn = '0' + standIn
    }
    return standIn;
  }
}
setInterval(clock, 1000);
</script>
<div class="clock"></div>