title: onreadystatechange() missing on XMLHttpRequest objects
body: <pre><code>(function (send) {
  
       XMLHttpRequest.prototype.send = function () {
  
           console.log(this.onreadystatechange); //null
           send.apply(this, arguments);
       };
  
  })(XMLHttpRequest.prototype.send);
  </code></pre>
  
  <p>Why is <code>this.onreadystatechange</code> null? According to <a href="https://developer.mozilla.org/en-US/docs/DOM/XMLHttpRequest" rel="nofollow">this</a> it should exist and be of type <code>function</code>.</p>