You can list what packages are installed globally in your system with npm -g list—shorthand for npm --global list—whereas you'd list the packages installed in an NPM project with npm list.

Let's see an example of what the command might return.

npm -g list
# /opt/homebrew/lib
# ├── cross-env@7.0.3
# ├── http-server@14.1.1
# ├── node-gyp@9.3.1
# ├── npm@9.5.0
# ├── pm2@5.2.2
# ├── spoof@2.0.4
# ├── ts-node@10.9.1
# └── typescript@4.9.5

nodemon is a tool that helps develop Node.js based applications by automatically restarting the node application when file changes in the directory are detected.

How to install it globally?

npm install -g nodemon

Then you can use it anywhere as nodemon script.js and, every time script.js changes, the execution will restart with the new code, avoiding repetitive calls to node script.js, for instance.