No, TEA (http://www.enetplanet.com/enc/) is not the kind of tool you can use for such a task. It is just a little bit more than a proof-of-concept or than a toy. TEA (like any other encryption system) cannot be actually used to encrypt/protect a javascript file that you send to the customer's browser.
Consider this: the user must have a copy of the encryption program to decypher the javascript file coming from your server. In other cases, this would not be a great security hole in itself. Any encryption system rely on the secretness of a key, not on the secreteness of the encryption program/algorithm.
Unfortunately, when talking of client-side javascript, this is a security hole. The encryption program (TEA) is a javascript file itself. Anybody can read it. It is trivial to modify it in a way that it just print out the encryption key or in a way that it just decrypt the "protected" javascript file without making any check.
Moreover, the end-user has total, unlimited access to the network comunication channel. He can just read the password (the key) with a network sniffer installed on its PC. No key (and no encryption system) can resist such an attack (well-known as a "man-in-the-middle" attack).
It is well known that there isn't any real way to encrypt/protect a javascript file. The best you can do is to obfuscate it.
If you really need to protect some kind of client-side software, you have to use compiled software (C/C++), encryption and some kind of hardware key. Any other system can easily be "cracked" (as the whole history of computer games can demonstrate).