'eslint' is not recognized as an internal or external command

I'm trying to install eslint & run it in vs code. I ran this command:

npm i -g eslint

and it seemed to work, but I keep keep getting a "'eslint' is not recognized as an internal or external command" error when I try & run eslint. What gives?

http://eslint.org/docs/user-guide/command-line-interface

http://eslint.org/docs/user-guide/getting-started