If you installed Node.js and npm using root permissions, you might end up with some nasty npm ERR! Error: EACCES errors as soon as you’re trying to install packages from npm. Consequently, you need to prefix your npm commands using sudo every time you want to install a package—which is anything but ideal. It seems that those problems are a result of using the .pkg installer provided on the Node.js website.
So, instead of running sudo npm install … each and every time, you can address the underlying issue by changing the permissions/ownership of two directories on your machine.
sudo chown -R `whoami` ~/.npm
sudo chown -R `whoami` /usr/local/lib/node_modules
Now you should be able to use npm without sudo.
