There are some nice online JavaScript debuggers like jsbin.com and jsfiddle.net, but if you want to edit a .js file that’s part of a version-controlled project, you’d probably prefer to do so in an IDE.

The Eclipse IDE has the JSDT plugin that provides syntax highlighting. (And it’s baked into the “Eclipse for Java EE Developers” edition, but can be installed in other versions, too.) To evaluate the code and see the output in the IDE’s Console view, some extra steps are necessary. Z0ltan’s guide is very helpful. Some extra hints:

1. Install nodeJs first. This is an executable that wraps Google’s V8 js engine, providing a commandline interpreter (and lots of useful libraries, I believe, such as allowing the coding of a web server using javascript). As of 2014 April 29, the Windows installer doesn’t broadcast through the OS that the Path has been updated, so as a workaround you may need to open the Environment Variables dialog and then close it with the OK button.
2. If you copy any text from Z0ltan’s page, or this one, into your IDE, make sure to re-type all the quotes; otherwise, copy/paste tends to pick up “fancy” quote characters that cause weird errors.
3. In between Z0ltan’s steps 1 and 2, you need to select “Program” in the left pane, and then hover over the buttons above it to select the one having hover text “New launch configuration”.
4. There’s a comment at the end of Z0ltan’s guide advising that you add the /D flag like this:

   /C "cd /D ${container_loc} && node ${resource_name}"
   

   if your js source file might be kept somewhere other than the C drive. But Microsoft’s documentation of cmd.exe flags just says /D disables autorun, so I’m not sure how helpful that is.

The NodeJs API pages start here, and there’s some helpful guidance on error-handling on Joyent.