Stopping countdown timer Javascript and invoking action

Question

I'm using this library to run a counter in JavaScript: https://github.com/mckamey/countdownjs

Here is what I have in my view:

<p id="countdown-holder", style="font-size:18px;"></p> 

<script>  
  var clock = document.getElementById("countdown-holder")  
  , targetDate = new Date(2015, 12, 10);  

  clock.innerHTML = countdown(targetDate).toString();  
  setInterval(function(){  
    clock.innerHTML = countdown(targetDate).toString();  
  }, 1000);  
</script> 

Currently, when the countdown finishes, it starts counting upwards.

How do I get the counter to stop when it hits 0 and display an alert(); message?

Answer 1

Inside your interval function check to see if Date.now() is greater than targetDate. If so, clear the timeout and display an alert.

var clock = document.getElementById("countdown-holder")  
var targetDate = new Date(2015, 7, 7);

var intervalId = setInterval(function(){
    if(Date.now() >= targetDate) {
      clearInterval(intervalId);
      alert('Hi.');
      return;
    }
    clock.innerHTML = (targetDate)
  }, 1000);

<div id="countdown-holder">
         
</div>