title: Javascript increment result of input and include comma
body: <p>I can't seem to get this working and it's driving me insane. I've made a JSFiddle and am keen for anyone with more knowledge than me to take a look! <a href="http://jsfiddle.net/kLQf3/9/" rel="nofollow">http://jsfiddle.net/kLQf3/9/</a></p>
  
  <p>Basically what I am trying to do is get the user to be able to put a figure (comma included) in the first "To" field ie. "60,000" and I want this number to display in the "From" field it incremented by 1 ie. "60,001".</p>
  
  <p>And the same for the input box. I have limited knowledge of JS but I've got the auto update working but the increment keeps giving me NaN errors because the comma is included.</p>
  
  <pre><code>window.onload = function () {
    var first = document.getElementById('firstFieldId'),
        second = document.getElementById('secondFieldId'),
        third = document.getElementById('thirdFieldId'),
        fourth = document.getElementById('fourthFieldId');
  
    first.onchange = function () {
      second.value = first.value;
    third.onchange = function () {
      fourth.value = third.value;
  };
  };
  };
  </code></pre>