title: Passing null in AJAX request Rails interprets it as "null"
body: <p>I am trying to send an AJAX request via the <a href="http://api.jquery.com/jQuery.ajax/" rel="nofollow">$.ajax</a> to a Rails 3 backend and I am stuck to a weird behavior. Take for example the following request:</p>
  
  <pre><code>$.ajax({
      url: $(this).attr('href'),
      type: 'PUT',
      dataType: "json",
      data: {a: null},
      success: function (data) {
          console.log("success!")
      }
  });
  </code></pre>
  
  <p>which I am binding to a click event. Simple. What is happening is that Rack parses the URI encoded form parameters as <code>{"a" =&gt; "null"}</code> and I really want to get parsed as <code>{"a" =&gt; nil}</code>. Is there any non-hackish way to achieve this behavior? </p>
  
  <p>Thanks a lot!</p>
  
  <p>P.S. If I pass <code>{a: undefined}</code> then params hash has no <code>a</code> key at all.</p>