Mac Osx: fix npm “EACCES: permission denied”

If you installed node from the pkg file from the official site, the npm executable is located in /usr/local/bin/npm and when you run an update (e.g. npm install -g npm@latest to upgrade npm itself) you get an error like this

npm ERR! code EACCES
npm ERR! syscall rename
npm ERR! path /usr/local/lib/node_modules/npm
npm ERR! dest /usr/local/lib/node_modules/.npm-i9nnxROI
npm ERR! errno -13
npm ERR! Error: EACCES: permission denied, rename '/usr/local/lib/node_modules/npm' -> '/usr/local/lib/node_modules/.npm-i9nnxROI'
npm ERR!  [Error: EACCES: permission denied, rename '/usr/local/lib/node_modules/npm' -> '/usr/local/lib/node_modules/.npm-i9nnxROI'] {
npm ERR!   errno: -13,
npm ERR!   code: 'EACCES',
npm ERR!   syscall: 'rename',
npm ERR!   path: '/usr/local/lib/node_modules/npm',
npm ERR!   dest: '/usr/local/lib/node_modules/.npm-i9nnxROI'
npm ERR! }
npm ERR!
npm ERR! The operation was rejected by your operating system.
npm ERR! It is likely you do not have the permissions to access this file as the current user
npm ERR!
npm ERR! If you believe this might be a permissions issue, please double-check the
npm ERR! permissions of the file and its containing directories, or try running
npm ERR! the command again as root/Administrator.

Then you can fix with this command that gives the owner permission with your username to the /usr/local directory.

sudo chown -R $(whoami) $(npm config get prefix)/{lib/node_modules,bin,share}

An alternative is installing via brew, but it sometimes takes too much time