Ubuntu 10.04 does not have a default node.js package. So if you want to use it, you need to install it manually:

sudo aptitude install git-core curl build-essential openssl libssl-dev
git clone https://github.com/joyent/node.git && cd node && git checkout v0.6.11
./configure
make
sudo make install
node -v

"v0.6.11" is the current release version of node.js. If you are not sure, run git tag to check which versions are available.

Up to this point, you are able to use the node command. You can then install npm which is a package manager of node.js its own:

curl http://npmjs.org/install.sh | sudo sh

After that, it's easy to install other node.js libraries. For example, to install uglifyjs, simply run:

sudo npm install uglify-js -g