A method to generate executable code randomly?

Is there a pre existing way to randomly create executable code? For instance, a generator that creates lines of random JavaScript code that is at least grammatically correct? It could generate each word or part of the code from a list of grammatical possibilities.

In the event that a generator like this doesn't exist, I'll probably program one myself. I checked the web and couldn't find anything close, anyway. I appreciate any suggestions or thoughts on the matter!