I really recommend you install node and npm using nvm. This is the fastest, cleanest and easiest way to do it.

That way, you install NVM simply doing:

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.5/install.sh | bash

To test that nvm was properly installed, close and re-open Terminal and enter nvm. If you get a nvm: command not found message, your OS may not have the necessary .bash_profile file. In Terminal, enter touch ~/.bash_profile and run the above install script again.

And you are now able to install node typing:

nvm install <version>

For example

nvm install 4.2.1

if you just want to install the latest node version, you can just type

nvm install node

In order to access node and npm as sudo (in order to have <1024 ports) you should run

n=$(which node)
n=${n%/bin/node}
chmod -R 755 $n/bin/* 
sudo cp -r $n/{bin,lib,share} /usr/local