Question

I’d like to make any file which begins with #!/usr/bin/env node be recognized as JavaScript.

I know Vim does this with other languages, like BASH, so there must be a way of doing it.

Thank you!

Answer 1

Add the following code snippet to your .vimrc or to another file
and source it in .vimrc:

if did_filetype()
  finish
endif
if getline(1) =~ '#!/usr/bin/env node'
  setfiletype javascript                                                      
endif

This simply sets the filetype to js when the first line of the
file matches ‘#!/usr/bin/env node’ – pretty much self explanatory.
This is described in the filetype help as well – check :he filetype