How to fix Node already installed but not linked issue on Mac?

To fix Node already installed but not linked issue on Mac, we change the permission of a few folders and run brew link.

To fix this, we

1. Run sudo chmod 776 /usr/local/lib to change the permission of the /usr/local/lib to make the folder readable, writable and executable.

2. Run brew link --overwrite node to link Node.

3. Run sudo chmod 755 /usr/local/lib to change the directory to be readable and executable.