title: Min and max in multidimensional array
body: <p>My array is:</p>
  
  <pre><code>var a = new Array();
  a[0] = {x: 10,y: 10};
  a[1] = {x: 20,y: 50};
  a[2] = {x: 30,y: 20};
  a[3] = {x: 10,y: 10};
  </code></pre>
  
  <p><code>var min = Math.min.apply(null, a.x)</code> doesn't work.
  Some ideas?</p>