You need to manually create a symlink /usr/bin/node. Shortcut for bash compatible shells:
sudo ln -s `which nodejs` /usr/bin/node
Or if you use non-standard shells, just hardcode the path you find with which nodejs:
sudo ln -s /usr/bin/nodejs /usr/bin/node
Later edit
I found this explanation in the link you posted
There is a naming conflict with the node package (Amateur Packet Radio Node Program), and the nodejs binary has been renamed from node to nodejs. You'll need to symlink /usr/bin/node to /usr/bin/nodejs or you could uninstall the Amateur Packet Radio Node Program to avoid that conflict.
Later later edit
It's been a while since I answered this. Although the solution I posted up here worked for me several times, users have reported a few more solutions within the comments:
From @user229115
sudo update-alternatives --install /usr/bin/node node /usr/bin/nodejs 10
From AskUbuntu (user leftium)
sudo apt-get --purge remove node
sudo apt-get --purge remove nodejs
sudo apt-get install nodejs