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Run Node.js REPL in Emacs


This program is derived from comint-mode and provides the following features.

  • token completion, same as Node.js REPL
  • file name completion in string
  • incremental history search
  • sending JavaScript codes to REPL


Put this file in your Emacs lisp path (e.g. ~/.emacs.d/site-lisp) and add the following line to your .emacs:

(require 'nodejs-repl)

Type M-x nodejs-repl to run Node.js REPL. See also comint-mode to check key bindings.

You can define key bindings to send JavaScript codes to REPL like below:

(add-hook 'js-mode-hook
          (lambda ()
            (define-key js-mode-map (kbd "C-x C-e") 'nodejs-repl-send-last-expression)
            (define-key js-mode-map (kbd "C-c C-j") 'nodejs-repl-send-line)
            (define-key js-mode-map (kbd "C-c C-r") 'nodejs-repl-send-region)
            (define-key js-mode-map (kbd "C-c C-c") 'nodejs-repl-send-buffer)
            (define-key js-mode-map (kbd "C-c C-l") 'nodejs-repl-load-file)
            (define-key js-mode-map (kbd "C-c C-z") 'nodejs-repl-switch-to-repl)))

When a version manager such as nvm is used to run different versions of Node.js, it is often desirable to start the REPL of the version specified in the .nvmrc file per project. In such case, customize the nodejs-repl-command variable with a function symbol. That function should query nvm for the Node.js command to run. For example:

(require 'nodejs-repl)
(defun nvm-which ()
  (let* ((shell (concat (getenv "SHELL") " -l -c 'nvm which'"))
         (output (shell-command-to-string shell)))
    (cadr (split-string output "[\n]+" t))))
(setq nodejs-repl-command #'nvm-which)

The nvm-which function can be simpler, and perhaps can run faster, too, if using Bash:

(defun nvm-which ()
  (let ((output (shell-command-to-string "source ~/.nvm/; nvm which")))
    (cadr (split-string output "[\n]+" t))))


Takeshi Arabiki (abicky)

Copyright and License

Copyright (C) 2012-2020 Takeshi Arabiki (abicky)

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see