Permission denied when installing npm modules in OSX

npm WARN checkPermissions Missing write access to /usr/local/lib/node_modules

Solution :
https://stackoverflow.com/questions/47252451/permission-denied-when-installing-npm-modules-in-osx

Option 1: Change the permission to npm’s default directory

1. Find the path to npm’s directory:
   • npm config get prefix
   • For many systems, this will be /usr/local
   • WARNING: If the displayed path is just /usr, switch to Option 2 or you will mess up your permissions.
2. Change the owner of npm’s directories to the name of the current user (your username):
   • sudo chown -R $(whoami) $(npm config get prefix)/{lib/node_modules,bin,share}
   • This changes the permissions of the sub-folders used by npm and some other tools (lib/node_modules, bin, and share).

Option 2: Change npm’s default directory to another directory

• There are times when you do not want to change ownership of the default directory that npm uses (i.e. /usr) as this could cause some problems, for example if you are sharing the system with other users.
• Instead, you can configure npm to use a different directory altogether. In our case, this will be a hidden directory in our home folder.

1. Make a directory for global installations:mkdir ~/.npm-global
2. Configure npm to use the new directory path:npm config set prefix '~/.npm-global'
3. Open or create a ~/.profile file and add this line:export PATH=~/.npm-global/bin:$PATH
4. Back on the command line, update your system variables:source ~/.profile

Test: Download a package globally without using sudo.