Regular Expressions via RPC
I have found the regular expression support in GWT (if not JavaScript in general) to be more limited than what I am used to from PHP. This is fine — it’s powerful enough for most form validation, and a nice tool to use for simple parsing. But there are times when that’s just not enough. In working on my RPC code, I had a head-slapping moment when I realized that it was just as easy to provide access to PHP functions like preg_match via RPC.
It certainly can simplify those situation where you just need to validate something significant. You can probably also get more regex power through JSNI, but I like sticking to higher level functionality. I’d no doubt program in a memory leak or some other irritating feature that would be painful to debug.