Path to Node.js Installation in Ubuntu

Quick explanation

You have a version with -pre. Get rid of it and put the latest stable version from nodejs.org.

You can use which to locate a command. For your case, type which nodejs.

EDIT: The answer from your link is referring to the path of node source code, not the nodejs binary.

On Ubuntu, most software can be installed from the built-in repositories. This updates it for you (even if it's sometimes a bit outdated).

To install the stable version the Ubuntu way, install the nodejs-legacy package (after uninstalling your version):

sudo apt install nodejs-legacy

To use the latest, refer to https://askubuntu.com/a/663052/438156 (my answer), or https://askubuntu.com/a/711976/438156 (bit more involved, more the Ubuntu way).