If you ever edit javascript code, the only emacs mode to consider is Steve Yegge’s JS2 mode.  The official page for it is here.  The annoucement page is here.  This javascript mode is an example of what more modes should aspire to.  It parses your buffer into a javascript AST and uses that for syntax highlighting, and also to check for syntactic correctness, helping to prevent you from having bugs caused by typos.  This is a lot faster than having to load the code into a web browser to find out that you missed a ‘;’.

It also provides Javascript code navigation.  Some other modes have this, like python mode (but not C-mode, at least not by default), but I wish all modes had it.

I wish someone would copy this strategy for a new C mode or Python mode.