title: Autofilling state and city based on zip code
body: <p>I am new to web development and I ran into an issue with a registration form that I'm building for our business. I am using this guide: <a href="http://css-tricks.com/using-ziptastic/" rel="noreferrer">http://css-tricks.com/using-ziptastic/</a>. This is my first experience with AJAX and JSON and I just can't get the city and state to autofill as soon as I'm done typing in the zip code. Any solutions/suggestions/alternatives will be much appreciated. I set up a basic jsfiddle to test everything out: <a href="http://jsfiddle.net/7VtHc/" rel="noreferrer">http://jsfiddle.net/7VtHc/</a></p>
  
  <p>HTML:</p>
  
  <pre><code>&lt;p&gt;Zip Code: &lt;input type="text" id="zip" /&gt;&lt;/p&gt;
  &lt;p&gt;City: &lt;input type="text" id="city" /&gt;&lt;/p&gt;
  &lt;p&gt;State: &lt;input type="text" id="state" /&gt;&lt;/p&gt;
  </code></pre>
  
  <p>jQuery, etc.</p>
  
  <pre><code>$("#zip").keyup(function() {
  var el = $(this);
  
  if ((el.val().length == 5) &amp;&amp; (is_int(el.val()))) {
      $.ajax({
      url: "http://zip.elevenbasetwo.com",
      cache: false,
      dataType: "json",
      type: "GET",
      data: "zip=" + el.val(),
      success: function(result, success)
  
      $("#city").val(result.city);
      $("#state").val(result.state);
      });
  }
  });
  </code></pre>