Question: how to do npm update?
Answer: npm -v. Upgrading on *nix (OSX, Linux, etc.) ... 
npm install -g npm@latest. Or upgrade to the most recent release:
npm install -g npm@next. Upgrading on Windows. ... 
npm config get prefix -g. ... 
npm config set prefix "${APPDATA}/npm" -g. ... 
npm config set prefix "${LOCALAPPDATA}/npm" -g.