I used JScrambler before and I really liked. If you don't mind the monthly fee, I'd say go for it.

They do nice stuff, like hiding some of your strings, other literals and random predicates inside an encrypted string. This is decrypted and eval'd at runtime using the text of the decrypt function as a parameter i.e, you can't beautify it otherwise it stop working. The random predicates are merged within your code for instance: it appends a `&& somePredicateThatReturnsTrue(someOtherRandomValue)` to ifs conditions. It makes it really hard to figure out what is happening.