cd ~
wget http://nodejs.org/dist/v6.2.1/node-v6.2.1-linux-armv6l.tar.gz
tar -xzf node-v6.2.1-linux-armv6l.tar.gz
node-v6.2.1-linux-armv6l/bin/node -v
The last command should print v6.2.1.
Now you can copy it to /usr/local
cd node-v6.2.1-linux-armv6l/
sudo cp -R * /usr/local/
For testing add /usr/local/bin to your path
export PATH=$PATH:/usr/local/bin
node -v
npm -v
This should print 6.2.1 and 3.9.3 for the versions of nodejs and npm. If you need a different version, just pick the one you like from the downloads.
Don't forget to add the PATH to your .bashrc to make it permanent.
To find the correct architecture, you can type uname -m
I have used
wget https://unofficial-builds.nodejs.org/download/release/v14.10.0/node-v14.10.0-linux-armv6l.tar.gz
for the latest node-js version to install it on my Raspberry Pi Zero W and it worked like a charm!