title: Error: Callback is not a function (nodejs)
body: <p>When I execute my code I keep getting the error 'TypeError: callback is not a function'.<br>
  This is the relevant code:   </p>
  
  <pre><code>exports.isVideo = function(tweetId, callback) {
    client.get('statuses/show/' + tweetId, function(err, tweet, res){
      if(tweet.extended_entities){
          if(tweet.extended_entities.media[0].type === 'video'){
              console.log('true');
              callback(true);
          } else {
              console.log('false');
              callback(false);
          }
      } else {
          console.log('false');
          callback(false);
      }
    });
  }
  </code></pre>
  
  <p>This is in a different file (I required the first file at the top of this one, that's not the reason for the error):   </p>
  
  <pre><code>ids.forEach(function(id){
      console.log(id.twitterId);
      twitterConverter.isVideo(id.twitterId, function(boolean){
          if(boolean){
              console.log('do something');
          } else {
              console.log('do nothing');
          }
      });
  });
  </code></pre>
  
  <p>First of all, please don't just mark this as duplicate because there are other posts with similar titles. I looked through them, and the reason was usually that no callback function was passed, or too many parameters were passed, which isn't the case here.  </p>
  
  <p>I'm not that experienced with nodejs yet, so maybe I'm overlooking something obvious, but I can't find what's wrong with this code.   </p>
  
  <p><code>client.get()</code> is from <a href="https://www.npmjs.com/package/twitter" rel="nofollow">this</a> npm package. Maybe the error has something to do with that?  </p>
  
  <p>I would be very glad if you could help me out here.</p>