title: JavaScript: Optional callback?
body: <p>I have coded a function, that has 3 arguments, one of them is a callback function.
  How do I make the callback an optional argument without having to code another function without the callback argument?</p>
  
  <pre><code>function myFunction(arg1, arg2, callback){
      // do something
  
      // callback() if it has been passed
  }
  </code></pre>