`jupyterlab` doesn't recognize `nodejs` and `npm` installations
The issue was with the version of nodejs installed. Ubuntu 16.04 LTS comes with v4.2.6. I've resolved the issue installing nodejs v6. If you need to install it in Ubuntu 16.04 LTS, you can follow this excellent tutorial.
try installing nodejs legacy using
sudo apt install nodejs-legacy
or alternatively you could
sudo ln -s /usr/bin/nodejs /usr/bin/node
the problem is that jupyter expects nodejs to be available using the command node which is not the case anymore