title: Difference between Array.apply(null, Array(x) ) and Array(x)
body: <p>What exactly is the difference between:</p>
  
  <pre><code>Array(3)
  // and
  Array.apply(null, Array(3) )
  </code></pre>
  
  <p>The first returns <code>[undefined x 3]</code> while the second returns <code>[undefined, undefined, undefined]</code>. The second is chainable through <code>Array.prototype.functions</code> such as <code>.map</code>, but the first isn't. Why?</p>