I am thinking about how some online services create dynamic JavaScript files. These files have the .js extension, but their content is not static. I found a sample file [here](http://j.maxmind.com/app/geoip.js). It seems that this script is generated with a higher level programming language. I think it is done with PHP or something similar, but I am not sure, and I have not found any documentation about this topic.

Is there any well known way to create these kind of dynamic JavaScript files?