title: Javascript for loop var "i" is treated as a string?
body: <p>I am using Titanium to build some mobile apps and I noticed that this will give a result that I wasn't expecting.  </p>
  
  <pre><code>data = ['a','b', 'c','d'];
  
  for (var i in data){
      Ti.API.debug(i+1);
  };
  </code></pre>
  
  <p>This will print: 01,11,12,13</p>
  
  <p>Is this something particular to Titanium or is it generally in Javascript?</p>
  
  <p>Why isn't 'i' being treated as an integer? I am very confused. </p>
  
  <p>Thanks for your help. </p>