title: Creating a custom block and writing the code to generate the Javascript code on Android
body: <p>I want a different category of blocks called <strong>'Movement'</strong> with two blocks inside it called <strong>MoveForward</strong> and <strong>MoveBackward</strong>.</p>
  
  <p>In the <strong>toolbox.xml</strong> file in blockly core library,
  I added the XML code for creating the UI.</p>
  
  <pre><code>&lt;category name="Movement" colour="190"&gt;
  
          &lt;block type="move_forward"&gt;
              &lt;value name="TEXT"&gt;
                  &lt;shadow type="text"&gt;
                      &lt;field name="TEXT"&gt;4&lt;/field&gt;
                  &lt;/shadow&gt;
              &lt;/value&gt;
          &lt;/block&gt;
  
          &lt;block type="move_backward"&gt;
              &lt;value name="TEXT"&gt;
                  &lt;shadow type="text"&gt;
                      &lt;field name="TEXT"&gt;4&lt;/field&gt;
                  &lt;/shadow&gt;
              &lt;/value&gt;
          &lt;/block&gt;
  
  &lt;/category&gt;
  </code></pre>
  
  <p>Now where do I need to add the JavaScript code that will create the output JavaScript code when these bocks are used and run ? 
  In simple terms, what extra I need to do to make these blocks generate the JavaScript code ?</p>