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