title: purpose of .bind(this) at end of ajax callback?
body: <p>From the reactjs tutorial, what's the purpose of having <code>.bind(this)</code> at the end of the ajax callback? Does code work correctly without it?</p>
  
  <pre><code>        data: JSON.stringify({text: text}),
          success: function (data) {
              this.setState({data: data});
          }.bind(this),
  </code></pre>