SpiderMonkey JavaScript and WebAssembly engine Shell Native Messaging Host

Installation and usage on Chrome and Chromium

1. Navigate to chrome://extensions.
2. Toggle Developer mode.
3. Click Load unpacked.
4. Select native-messaging-spidermoney-shell folder.
5. Note the generated extension ID.
6. Open nm_spidermonkey.json in a text editor, set "path" to absolute path of nm_spidermonkey.js and chrome-extension://<ID>/ using ID from 5 in "allowed_origins" array.
7. Copy the file to Chrome or Chromium configuration folder, e.g., Chromium on *nix ~/.config/chromium/NativeMessagingHosts; Chrome dev channel on *nix ~/.config/google-chrome-unstable/NativeMessagingHosts; and similar for Chrome For Testing.
8. Make sure nm_spidermonkey.js is executable. To download SpiderMonkey shell

wget --show-progress \
--progress=bar \
--output-document jsshell.zip \
https://archive.mozilla.org/pub/firefox/nightly/latest-mozilla-central/jsshell-linux-x86_64.zip \
&& unzip jsshell.zip \
&& rm jsshell.zip

or using jsvu

bun install jsvu
./node_modules/.bin/jsvu --os=linux64 --engines=spidermonkey

and use the appropriate path to the js or spidermonkey executable, respectively in nm_spidermoney.js, e.g.,

#!/usr/bin/env -S /home/user/bin/js

or

#!/usr/bin/env -S /home/user/.jsvu/engines/spidermonkey/spidermonkey

9. To test click service worker link in panel of unpacked extension which is DevTools for background.js in MV3 ServiceWorker, observe echo'ed message from SpiderMonkey Native Messaging host. See Notes.

Notes

SpiderMonkey JavaScript/WebAssembly engine Shell does not expect to be used as a Native Messaging host. Standard input and standard output are not specified by ECMA-262. We have to work around that fact in this js shell.

JavaScript runtimes tested so far, include QuickJS, txiki.js, Deno, Node.js, Bun. Each process standard input and output differently. With the aforementioned runtimes we can maintain a persistent connection between client and host using connectNative(). See NativeMessagingHosts.

While we use connectNative here instead of sendNativeMessage that is only to send a trailing "\r\n\r\n" for readline() to stop reading (blocking), echo the message back then call disconnect(), repeat for each message, to avoid the js shell hanging on subsequent messages from client to host.

For the above reasons native-messaging-spidermonkey-shell will not be added to the working Native Messaging hosts repository listed above until we get this working as intended.

For differences between OS and browser implementations see Chrome incompatibilities.

License

Do What the Fuck You Want to Public License WTFPLv2