Enables tab-completion in all npm commands.
The synopsis above
loads the completions into your current shell. Adding it to
your ~/.bashrc or ~/.zshrc will make the completions available
You may of course also pipe the output of npm completion to a file
such as /usr/local/etc/bash_completion.d/npm if you have a system
that will read that file for you.
When COMP_CWORD, COMP_LINE, and COMP_POINT are defined in the
environment, npm completion acts in "plumbing mode", and outputs
completions based on the arguments.