first you'll need to make sure your system has a c compiler. For OSX, XCode will work, for Ubuntu, the build-essential and libssl-dev packages work.
git clone https://github.com/creationix/nvm.git ~/.nvm
source ~/.nvm/nvm.sh
nvm install 0.10
nvm use 0.10
nvm alias default 0.10
it's a good idea to put the 2nd line in your ~/.bashrc, ~/.zshrc, ~/.profile, etc to source nvm automatically upon login.
git clone https://github.com/holonomy/leveldb-react-example
npm install
npm run start
browse to localhost:5000
npm run develop