You can build many apps using node.js and npm on your raspberry pi and it's very easy to interact with GPIO or other components connected to your raspberry pi. So if you are like me and like to do it on node.js here a few simple steps to install node and npm.
Step 1: Detect What Version of Node.js You Need
The processor on Raspberry Pi is ARM, but depends on the model there can be ARMv6, ARMv7 or ARMv8. This 3 versions of ARM is supported by Node.js.
So first of all type this in your terminal on raspberry pi to detect the version that you need:
If the response starts with armv6 than that's the version that you will need. For example for raspberry pi zero W you will need ARMv6
Step 2: Download Node.JS Linux Binaries for ARM
Go to node.js download page and check right click on the version of ARM that you need and choose Copy Link address.
After that in the terminal using wget download the tar.gz file for that version. Just type wget, paste the link copied before and make sure the extension is .tar.gz. If it's something else change it to this and it should be ok. For example I will need ARMv6 and I will type this in my terminal:
Step 3: Extract the Archive
Using tar that is already installed with the system on your raspberry pi just type this (make sure you change the filename with the file that you have)
tar -xzf node-v8.9.0-linux-armv6l.tar.gz
Step 4: Copy Node to /usr/local
sudo cp -R * /usr/local/
Step 5: Check If Everything Is Installed Ok
Check if node and npm are installed correctly. This lines should print the version of node and npm installed.
Now you have node.js installed on your Raspberry Pi and working so you can build something using node