There are so many different ways todo this.
curl -sLS https://apt.adafruit.com/add | sudo bash; sudo apt-get install node
Its easy, works and by a team I trust.
Swapping node versions
Node has lots of different versions and moves faster than most package managers (apt-get) can keep up, so using an extra tool to keep things fresh is handy.
I recommend using
nvm - Node Version Manager, its simple and does what it says on the tin.
This lets you run
nvm and select what version of node you want to run.
I currently use node 4.
nvm install v4. Simple.