title: How to generate a four digit code (i.e 0001) javascript
body: <p>I need to autogenerate a new four digit code that everytime I run the function the value increments. Such as 0001 the first time, 0002, 0003 and so on.
  This is the code I have so far, the format is okay but I cant get it to increment the value automatically. I know it's probably a while loop but I wanted to ask advise on how it should be done. Thank you.</p>
  
  <pre><code>function pad(n){
  
  var num = 1;
  var string = "" + num;
  var pad = "0000";
  n = pad.substring(0, pad.length - string.length) + string;
  num++;
  return n;
  }
  </code></pre>