title: Add array to two-dimensional array
body: <p>Array A is a two dimensional array. It's made up of array X and Y. I'd like to add array Z to Array A as another item in Array A. How do I do this?</p>
  
  <p><strong>Edited</strong> to add code:</p>
  
  <pre><code>arrayA = new Array(
      [1, 2, 3] //array x
      [4, 5, 6] //array y
      );
  
  arrayZ = new Array(7, 8, 9);
  
  //now, how do I add arrayZ onto the end of arrayA?
  </code></pre>