Q:

Extend ObjC class without modifyng its .m nor .h ? JS prototype style?

Is it possible to add methods to an ObjC class without modifying its .h nor .m files?
In JavaScript, you can for instance add a method to a prototype from anywhere, take for instance adding a method to the Array prototype:
Array.prototype.stackOverflow = function(parameters);

A:

You can use categories.
The Objective-C Programming Language: Categories and Extensions

