title: dataType: 'json' vs data: JSON.stringify(obj) in $.ajax
body: <p>I have this data structure:</p>
  
  <pre><code>var formValues = {
          TemporaryToken: a.userStatus.get("TemporaryToken"),
          MemorableWordPositionAndValues:[
              {
                  Position: a.userStatus.get("MemorableWordPositions")[0],
                  Value: this.$('[name="login-memorable-character-1"]').val()
              },
              {
                  Position: a.userStatus.get("MemorableWordPositions")[1],
                  Value: this.$('[name="login-memorable-character-2"]').val()
              },
              {
                  Position: a.userStatus.get("MemorableWordPositions")[2],
                  Value: this.$('[name="login-memorable-character-3"]').val()
              }
          ]
      }
  </code></pre>
  
  <p>And when I send it with $.ajax like so:</p>
  
  <pre><code>$.ajax({
          url:url,
          type:'PUT',
          //dataType:"json",
          data: JSON.stringify(formValues),
          success:function (data) {
  
          }
      });
  </code></pre>
  
  <p>It sends the request. However, if I send it like so:</p>
  
  <pre><code>$.ajax({
          url:url,
          type:'PUT',
          dataType:"json",
          data: formValues,
          success:function (data) {
  
          }
      });
  </code></pre>
  
  <p>I receive a 400 Bad Request. Is this a problem on the server or is JSON.stringify doing something different to just setting the dataType to 'json'?</p>