GNU ELPA - firefox-javascript-repl


Jack into Firefox
firefox-javascript-repl-0.9.5.tar (.sig), 2024-Mar-31, 100 KiB
Thomas Fitzsimmons <>
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To install this package from Emacs, use package-install or list-packages.

Full description


Start the REPL:

M-x firefox-javascript-repl RET

To stop the REPL, kill the *firefox-javascript-debugger* buffer:

C-x k RET yes RET

or quit Firefox from within Firefox.


REPL into a new Firefox instance's JavaScript engine.  A new
throwaway Firefox profile directory is created before each run, so
you won't need to modify your existing profiles.  This mode takes
care of starting the new Firefox process in debugging mode, which
may be tedious to do by hand.

This `comint' mode is barebones and unstructured, meant for quick
JavaScript experiments.  On newer versions of Emacs with
`comint-indirect-buffer' support, syntax highlighting happens on
the current statement.

Paste each statement from `example.js' into the REPL to try it out.

For projects you should probably use `dap-mode' and `lsp-mode'

Only Firefox and Firefox-derivative browsers will ever be supported
(unless someone sends a really convincing patch).  I promise to
attempt to stive to keep this working with at least the
greenest-of-evergreen Firefox and Firefox ESR versions (see
Compatibility).  My sense is that the Firefox Remote Debugging
Protocol is less of a moving target than it used to be.  Emacs
versions back to 26.1 (or earlier if anyone can test on Emacs <
26.1) will be supported.

Wouldn't it be great (for other people) to turn this into a full
SLIME analog for JavaScript (patches accepted)?  I tried `jsSlime'
( but its most recent update is ten
years old and the Firefox Remote Debugging Protocol has changed too

The function `fjrepl--extract-result' could do a way better job of
getting results but I find it OK for little experiments.  If I need
more information I submit a more precise JavaScript statement.
Syntax errors currently fail silently.


M-x package-install RET firefox-javascript-repl RET


║  Test Date ║ Browser  ║ Version              ║
║ 2023-05-26 ║ Firefox  ║ 102.11.0esr (64-bit) ║
║ 2023-05-26 ║ Firefox  ║ 113.0.2 (64-bit)     ║
║ 2023-05-26 ║ Abrowser ║ 111.0.1 (64-bit)     ║


FRDP: Firefox Remote Debugging Protocol

Old versions

firefox-javascript-repl-0.9.4.tar.lz2023-Jun-0227.2 KiB
firefox-javascript-repl-0.9.3.tar.lz2023-Jun-0227.2 KiB
firefox-javascript-repl-0.9.0.tar.lz2023-Jun-016.57 KiB


GNU Emacs firefox-javascript-repl NEWS -- history of user-visible changes.

* New in firefox-javascript-repl 0.9.5

Released 2023-06-05:

** Use browse-url to find firefox binary.

* New in firefox-javascript-repl 0.9.4

Released 2023-06-02:

** Prompt before deletion of temporary profile directory

* New in firefox-javascript-repl 0.9.3

Released 2023-06-01:

** Autoload firefox-javascript-repl

** Include local copy of wtfjs