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Not that I know much about bot coding (for those who know the "wumpus world", my agent had a passion for running into walls), the learning curve would depend on how well you understand object orientation and pointers for C++. I haven't really touched JavaScript, but I'm well versed in Java, so if they're similar you shouldn't have any large difficulties with C++ (just have to remember that it won't garbage collect for you).
C++ also isn't a scripting language (well, according to my definitions anyway), though the syntax may look similar.
Hope that helps a little. If not, sorry!