To minimize the chance of permissions errors, you can configure npm to use a different directory. In this example, you will create and use hidden directory in your home directory.
1.Back up your computer.
2.On the command line, in your home directory, create a directory for global installations:
mkdir ~/.npm-global
3.Configure npm to use the new directory path:
npm config set prefix '~/.npm-global'
4.In your preferred text editor, open or create a ~/.profile file and add this line:
export PATH=~/.npm-global/bin:$PATH
5.On the command line, update your system variables:
source ~/.profile
or
source ~/.bash_profile
6.To test your new configuration, install a package globally without using sudo:
npm install -g jshint
Instead of steps 2-4, you can use the corresponding ENV variable (e.g. if you don’t want to modify ~/.profile):
NPM_CONFIG_PREFIX=~/.npm-global
Reference from
https://docs.npmjs.com/resolving-eacces-permissions-errors-when-installing-packages-globally
