Node.js is an open-source, cross-platform JavaScript runtime environment for developing a diverse variety of tools and applications. Although Node.js is not a JavaScript framework, many of its basic modules are written in JavaScript, and developers can write new modules in JavaScript. The runtime environment interprets JavaScript using Google’s V8 JavaScript engine.

— Wikipedia

For this installation and future NodeJS upgrades we will use npm.

npm consists of a command line client that interacts with a remote registry. It allows users to consume and distribute JavaScript modules that are available on the registry. Packages on the registry are in CommonJS format and include a metadata file in JSON format. Over 280,000 packages are available on the main npm registry.

— Wikipedia

If this is a fresh Ubuntu install,
go ahead and enable and secure your OpenSSH server on Ubuntu 16.04 LTS

Login to your server and pull the latest versions of the available packages:

sudo apt update

If you wish to upgrade all packages (recommended for fresh installs) also run:

sudo apt upgrade

Ok, so now we can begin the actual installation for our NodeJS Environment:

sudo apt install npm
sudo npm cache clean -f
sudo npm install -g n

If there are no errors you can proceed to upgrading NodeJS to the latest version:

sudo n stable

OR install a specific version like so:

sudo n 4.4.6

Finally you must create a symlink for NodeJS:

ln -sf /usr/local/n/versions/node//bin/node /usr/bin/node

Now you should have both NodeJS and npm installed and ready to use. You can check your installed versions using:

node -v
npm -v

Footnote:

If you want your NodeJS apps to be able to listen on port 80, then you should execute:

apt install libcap2-bin

After the installation is done, run:

sudo setcap cap_net_bind_service=+ep `readlink -f `which node``

THAT’S IT!