How to completely remove Node.js and reinstall it on Mac OS X

Hello, colleagues! I'm a beginner in JavaScript and Node.js. I started learning development on a MacBook, but it seems I messed up the Node.js installation.

First, I installed Node.js via the official installer from the website. Then, when I needed to update the version, I simply downloaded a new installer and ran it over the old installation. Now I have a complete mess: the node -v command shows one version, npm -v shows another, and the global packages I installed sometimes work and sometimes don't.

I tried to remove Node.js manually, deleting folders from /usr/local/lib/node_modules, but it seems I only made things worse. Now npm has stopped working altogether with errors like Error: Cannot find module.

I want to completely clean the system of all traces of Node.js and