I\'ve literally searched everything on web. But I could not find the solution for the error node-0.8.8 already installed, it\'s just not linked. Is it related t
hardcorepunk's answer worked. However, we can no longer chown /usr/local in High Sierra. So, execute the commands in this order:
sudo brew uninstall node
brew update
brew upgrade
brew cleanup
brew install node
sudo chown -R $(whoami) $(brew --prefix)/*
brew link --overwrite node
brew postinstall node