How to determine if npm module installed in bash

Question

My objective is to only install this npm package if it's not already available. This continues to to execute even when I've installed the module globally.

if [ npm list -g widdershins &> /dev/null ] || [ ! -d node_modules ]; then
    npm install widdershins --no-shrinkwrap
fi

How can I adjust this to detect when it's installed globally?

Answer 1

if you want a one liner:

Local

npm list | grep widdershins || npm install widdershins --no-shrinkwrap

Global:

npm list -g | grep widdershins || npm install -g widdershins --no-shrinkwrap