title: Why does this callback return undefined?
body: <pre><code>function firstFunction(num, callback) {
    callback(num);
  };
  
  function secondFunction(num) {
    return num + 99;
  };
  
  console.log(firstFunction(56, secondFunction));
  </code></pre>
  
  <blockquote>
    <blockquote>
  <pre><code>undefined
  </code></pre>
    </blockquote>
  </blockquote>
  
  <p>If I call <code>console.log</code> from within <code>secondFunction</code>, it returns the value. </p>
  
  <p>Why not? What's the point of setting up callbacks if I can't get the value out of them to use later? I'm missing something.</p>