title: callback() or return callback()
body: <p>It's possible I don't understand Node's event loop well enough. </p>
  
  <p>Say I have a function <code>foo</code> which contains an asynchronous function <code>async_func</code>. Do I have</p>
  
  <pre><code>//1
  function foo(callback) {
         //stuff here
         async_func(function() {
              //do something
              callback();
         });
  //this eventually get executed
  }
  </code></pre>
  
  <p>or</p>
  
  <pre><code>//2
  function foo(callback) {
         //stuff here
         async_func(function() {
              //do something
              return callback();
         });
  //never executed
  }
  </code></pre>