Jquery - Variable Increment +1

I've had a look round and I'm a little confused. There seems to be several responses to my particular problem but I don't fully understand. So if anybody could help that'd be grea

Solution 1:

var counter = 1;

setInterval(function() {

  var _text = counter + "<br>";

  $("div").append(_text);

  counter++;   
   
},5000);

<scriptsrc="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script><div></div>

If you want it to replace the old number use .html() instead of .append()

"01" is a string, 1 is a number you can increment.

Solution 2:

If you just need zero padding:

functionpad(num, size) {
    var s = num+"";
    while (s.length < size) s = "0" + s;
    return s;
}

var thumbNumber = "02";

thumbNumber = parseInt(thumbNumber);
var nextNumber = pad(++thumbNumber,2);

console.log(nextNumber);

Live Demo -- http://jsfiddle.net/v02vgw6w/2/