title: javascript : Merge two arrays into one
body: <p>Say for example I have an array</p>
  
  <pre><code>arr = [
   1, 2, 3
   4, 5, 6
  ]
  </code></pre>
  
  <p>Instead, I would like to use aliases for each line
  Ex.</p>
  
  <pre><code>var a = [ 1, 2, 3 ];
  var b = [ 4, 5, 6 ];
  </code></pre>
  
  <p>Where</p>
  
  <pre><code>arr = [
   a,
   b
  ]
  </code></pre>
  
  <p>should be the same as the original <code>arr</code>.</p>
  
  <p>Yet the current example gives back <code>[ [1,2,3],[4,5,6] ]</code> instead</p>
  
  <p>How would I achieve something like this in javascript?</p>