title: $.extend not working with arrays with in objects
body: <p>Facing problem while changing array with in extended object in jquery.</p>
  
  <p><strong>Example:</strong></p>
  
  <pre><code>var a = {}, b = {j: 2, arr : [{1:1}]};
  
  $.extend(a, b);
  
  console.log("A=" ,a);
  console.log("B=" , b);
  
  b.arr.push({2:2});
  
  console.log("A=" , a);
  console.log("B=" , b);
  </code></pre>
  
  <p><strong><em>Link:</strong> <a href="http://fiddle.jshell.net/GopsAB/BZu7S/1/" rel="nofollow">http://fiddle.jshell.net/GopsAB/BZu7S/1/</a></em></p>
  
  <p><strong>Expected:</strong>
  object a should not changed while change b.</p>