# Pure JavaScript kernel

**URL:** <https://discourse.jupyter.org/t/pure-javascript-kernel/38353>\
**Category:** Kernels\
**Created:** [January 24, 2026, 12:50pm UTC](https://discourse.jupyter.org/t/pure-javascript-kernel/38353 "2026-01-24T12:50:28Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Migwell](https://yyz1.discourse-cdn.com/flex031/user_avatar/discourse.jupyter.org/migwell/32/21564_2.png) [@Migwell](https://discourse.jupyter.org/u/Migwell)\
**Post date:** [January 24, 2026, 12:50pm UTC](https://discourse.jupyter.org/t/pure-javascript-kernel/38353/1 "2026-01-24T12:50:28Z")

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I haven’t wrapped my head about the Jupyter architecture, but it seems feasible to have a pure JavaScript kernel. Has there been any initiative or planning to do this? If not, how come?

I’ve found [widgetti/ipyreact](https://github.com/widgetti/ipyreact/), but this doesn’t succeed in removing Python from the workflow.

I can imagine a few use cases for this. It might be useful for learning or teaching JavaScript/TypeScript, or it could be used to add the rich library of web components to notebooks. This could also remove the need to Python wrappers around JavaScript code. For example I’m currently using `ipyleaflet` in my notebook in order to get an interactive map, but using `Leaflet` directly, without Python, would be simpler and better remain in sync with upstream Leaflet.

Technically I guess the kernel backend could be a separate node process, or it could be the browser’s own JavaScript engine in a similar way to Pyodide running in the browser.

As I understand, React is already used in the frontend of `ipykernel`, does this make everything easier?

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**Author:** ![bollwyvl](https://yyz1.discourse-cdn.com/flex031/user_avatar/discourse.jupyter.org/bollwyvl/32/904_2.png) [@bollwyvl](https://discourse.jupyter.org/u/bollwyvl)\
**Post date:** [January 24, 2026, 1:30pm UTC](https://discourse.jupyter.org/t/pure-javascript-kernel/38353/2 "2026-01-24T13:30:07Z")

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> pure

That’s part of the fun part, is folk agreeing on what exactly that is. The definition I like, which coincides with this use case, is “the JS supported by browsers,” with all its warts, specifically, “the one currently supported by Firefox LTS,”

Anything `node`/`deno`/`bun`/`quickjs` wouldn’t be any closer to `import "leaflet"` and actually being able to do proper slippy maps in the DOM… unless it re-invented everything that widgets do by separating compute and display.

> the browser’s own JavaScript engine

Presently, the two JupyterLite [javascript](https://github.com/jupyterlite/javascript-kernel/) [kernels](https://github.com/jupyter-xeus/xeus-javascript) run in WebWorkers. While still possible, this reduces the chance of fully bricking your editor experience because of a runaway `while` loop, but means they don’t have access to the same DOM as a `leaflet` instance. Some work is underway to offer an `iframe`-based kernel which would be; not sure about the `xeus` one.

> React is already used in the frontend

`react` is indeed involved (and difficult to avoid) in the `@jupyterlab/ui-components`-based clients such as JupyterLite, Notebook 7+ and JupyterLab itself, but the relationship has never been all that smooth… but the “react is life” thing was tried on the `nteract` stack, and never really caught on.

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**Author:** ![Migwell](https://yyz1.discourse-cdn.com/flex031/user_avatar/discourse.jupyter.org/migwell/32/21564_2.png) [@Migwell](https://discourse.jupyter.org/u/Migwell)\
**Post date:** [January 24, 2026, 1:46pm UTC](https://discourse.jupyter.org/t/pure-javascript-kernel/38353/3 "2026-01-24T13:46:55Z")

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Thanks, so there are some existing kernels, but they’re not able to actually render elements because they can’t access the DOM. I guess I’m happy to take the risk of the code breaking my browser because I’m the author, and because the exported notebook that I share with my end user is frozen and won’t be running the code on their machine. For now I’ll probably wait to see what happens with `jupyterlite/javascript-kernel`, because iframe rendering sounds promising.