This config assumes you're using use-package to manage packages.
(use-package add-node-modules-path
:ensure)
(use-package eslint-fix
:ensure)
(use-package coffee-mode
:after (add-node-modules-path)
:config
(add-hook 'coffee-mode-hook 'add-node-modules-path)
(add-hook 'coffee-mode-hook (lambda () (add-hook 'after-save-hook 'eslint-fix nil t)))
:ensure)