Answer by CHsurfer for nodejs vs node on ubuntu 12.04

This happened to me as well.

node -v => 0.10.2
nodejs -v => 5.5.0

The issue was that I had installed node from source some time ago. Running

which node

always pointed to this local installation. Also,

echo NODE_PATH

pointed to the local installation.

deleting the directory with the source install didn't help. It just broke the node command. In the end, unsetting the NODE_PATH environmental variable and purging then reinstalling nodejs did the trick.

unset NODE_PATH
sudo apt-get --purge remove nodejs
sudo apt-get install nodejs

After this,

node -v => 5.5.0

and npm install started to work for packages depending on Node => 5.0.