title: JS API documentation [, arg ] vs , [ arg ]
body: <p>When reading the documentation for various APIs I've noticed that sometimes a function definition will be written like this:</p>
  
  <pre><code>jQuery.getJSON( url [, data ] [, success( data, textStatus, jqXHR ) ] )
  </code></pre>
  
  <p>and sometimes like this:</p>
  
  <pre><code>jQuery.getJSON( url, [data], [success( data, textStatus, jqXHR )] )
  </code></pre>
  
  <p>Does putting the commas inside the brackets have a different meaning than outside the brackets?</p>