title: How to make callback function in Coffeescript
body: <p>I can't find out how to make a function that calls another function at the end.</p>
  
  <p>I want to be able to do something like this:</p>
  
  <pre><code>book.save (err) -&gt;
    MyFunc param1, param2, (callbackParam) -&gt;
      # some code using callbackParam
  
  MyFunc = (param1, param2) -&gt;
    # some other code that defines callbackParam
    ?.call(callbackParam)
  </code></pre>
  
  <p>What has to be called and how does it receive the data?</p>