Installing NPM to avoid using sudo on Mac OS X El Capitan. Node.js installed via https://nodejs.org/en/

gistfile1.txt

$ node -v
v6.9.5

$ which gcc
/usr/bin/gcc

$ npm -v
3.10.10

$ mkdir "${HOME}/.npm-packages"
$ echo NPM_PACKAGES="${HOME}/.npm-packages" >> ${HOME}/.bashrc
$ echo prefix=${HOME}/.npm-packages >> ${HOME}/.npmrc
$ echo NODE_PATH=\"\$NPM_PACKAGES/lib/node_modules\:\$NODE_PATH\" >> ${HOME}/.bashrc
$ echo PATH=\"\$NPM_PACKAGES/bin\:\$PATH\" >> ${HOME}/.bashrc
$ echo source "~/.bashrc" >> ${HOME}/.bash_profile
$ source ~/.bashrc

Note: mostly taken from from https://johnpapa.net/how-to-use-npm-global-without-sudo-on-osx/
Note: Node.js installed via their OS X installer as per the description (above).

Run checks:

$ nano ~/.npmrc
$ nano ~/.bashrc
$ nano ~/.bash_profile

All should work as per https://johnpapa.net/how-to-use-npm-global-without-sudo-on-osx/

See also: https://github.com/sindresorhus/guides/blob/master/npm-global-without-sudo.md