Why does JSF deliver JavaScript ressources with the file extension .jsf and GET parameter ln=js? -

for example:

<h:outputscript library="js" name="foo.js" /> 

becomes:

<script type="text/javascript"     src="/helloworld/javax.faces.resource/foo.js.jsf?ln=js"></script> 

note .jsf?ln=js part.

why that?

i think .jsf causes jsf servlet take control on how resource download , hence allows library versioning.

see: what jsf resource library , how should used?