Посмотрел, возможности достаточно интересные, но сразу смутило то, что работает только под Windows и Mac... Спасибо, посмотрю поподробнее что там внутри.
1. JS include files can be checked by JSLint and PHP by Code_Sniffer before Selenium to make sure syntax and coding standards are fine.
My link points to a way to check JS after is was build by PHP into HTML but before it was sent to browser. You are right you will not test it inside browser. This is to check JS which is embedded into PHP code - this can not be checked with step 1.
Can you post page sample with what you want to catch? Something which is fine in one browser but brakes another one when loaded into it?
I will check it with Lint before sending to browser and think on how to catch it in browser if JSlint will not.