Last Updated: 2025-10-30

I wanted to switch from a regular JavaScript file to my JavaScript test in Vim using the command ':A' as provided by a plugin called alternate_js.

The issue was that this command :A also existed in rails.vim. This took me too long to figure out. What are some better ways in future:

• :debug A - run command step by step in a debugger (use "step" or "next")
• [functions only] :12verbose call MyFunction() - give verbose level 12 (every sub-function call) for just MyFunction. You might also want to sent this output to a file, lest it overwhelm you: set verbosefile=debug.txt

Other times you want to debug some key mapping (e.g. to ensure it's not already taken up). For example, to debug the <tab> key mapping for insert mode, use the command :verbose imap <tab>