title: Extra parameters in a self executing function?
body: <p>I saw this piece of code in a webpack compiled file</p>
  <pre><code>(1,2, function(x) {
      console.log(x);
      return 4;
  })(5);
  </code></pre>
  <p>This seems to execute correctly. I am aware the <code>5</code> is a parameter to <code>function(x)</code></p>
  <p>I don't understand what the <code>1</code>,<code>2</code> are? How is this valid?</p>