After being in the learning Phase for soo long, i am looking to start a small Web Application in ocaml.
However, one requirement is “allow userscripts” i.e in the app users will write scripts (in javascript) and the application will execute them for some decision making on behalf of the user.
i am not able to find any library/way to accomplish this, what i am basically asking is a Nashorn/Rhino (in JVM) equivalent.
Any pointers?, Thanks
Cross post in reddit: Help Regarding Embedded Javascript : ocaml
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I’m not sure about OCaml-specific options, but there’s a whole slew of options for running embedded JS/WASM. A few that I’m aware of:
Fabrice Bellard’s QuickJS. This is an excellent option using a no-dependency C library (and the engine itself can be compiled to WASM). I have some experience compiling it to WASM and running in-browser for its built-in arbitrary precision numerics functionality, but haven’t used it via OCaml.
You could expose an API to raw WASM modules which you can then load at runtime in your web app. Alternatively, if you’re willing to take on some heftier dependencies, you could use a system like Extism to handle much of the glue. I don’t have experience with Extism itself, but they do have an OCaml host SDK. Getting it to work in the browser will probably require additional gymnastics and darker JSOO corners. (Note that you can always use the backdoor of adding a JS shim for plugin code and then importing that into your OCaml code.)
Finally, if you really want to stick to vanilla JS (no additional compilation step, etc.) and no dependencies, you can fall back to running the user/plugin code in an isolated context, e.g., using iframes. The primary downside of this approach is that it forces all of your plugin interop to be asynchronous (communication happens by message passing). This might be more annoying for you and could be tricky with various CSP enforcements depending on how you’re deploying. However, it’s the lightest-weight option in terms of content delivery (no WASM binaries or dependencies to ship) and also only requires users to write JS.
I just realized that you didn’t actually clarify where the user code will be executing. I assumed in-browser, but if you’re running a stateful backend that user code will be executed on, then the Extism OCaml SDK could be a good fit (though I might still prefer QuickJS, depending on what kind of functionality you need).
I am looking run this(user Js) in the backend, not the browser, i will have a look at the Extism, Thanks