Since npm itself is a Node.js module, it can be updated using itself.
If OS is Windows must be running command prompt as Admin
npm install -g npm@latest
If you want to check for updated versions you can do:
In order to update a specific package:
npm update <package name>
This will update the package to the latest version according to the restrictions in package.json
In case you also want to lock the updated version in package.json:
npm update <package name> --save
Found a mistake? Have a question or improvement idea?
Let me know.