JS Generators: How is `return yield` different from `yield`? : <pre><code>function* foo() {
  yield 123
};

// - - -

function* foo() {
  return yield 123
};
</code></pre>

<p>I can’t seem to demonstrate the difference between the two.</p>

<ul>
<li>Is there a demonstrable difference?</li>
<li>Should <code>return</code> be used in a generator?</li>
</ul>
