If you have a very big application written in Javascript, there's only IntelliJ Idea. It parses multiple Javascript files and highlights not only syntax errors but undeclared variables and functions, allows to jump from function call to function definition, and more.
I've tried Emacs (because that's my favorite editor) and Komodo, and they don't come close. I guess it's the same for Eclipse.
Personally, I think that superior parsing and navigation abilties of Idea are only required when you're working with crappy undocumented code, otherwise I'd happily write the code in Emacs using js2-mode, but I'm working with huge poorly documented and buggy framework and it really helps to be able to jump to the source of the function or superclass to check how they work.
