The preferred method for installing Node.js, now, is to use the versions available in package managers, such as apt-get, or MacPorts. Package managers simplify your life by helping to maintain the current version of the software on your computer, ensuring to update dependent packages as necessary, all by typing a simple command such as apt-get update. Let's go over this first.
Installing Node.js using package managers
Installing on macOS with MacPorts
The MacPorts project (http://www.macports.org/) has for years been packaging a long list of open source software packages for macOS, and they have packaged Node.js. After you have installed MacPorts using the installer on their website, installing Node.js is pretty much...