Is there a limit to javascript's eval, like in lenght?

I'm trying to build an app where you can store JS code in the DB, which you can later load and eval in order to execute it, but i'm reaching a limit. First of all, the code has to all be in one line. Any multiline statements are not executed. Next, i'm reaching a limit in length (i guess). If i execute the code manually, it works, but put that same code in the db, load it via ajax, and try to execute it, and it fails.

Any ideas why?