Or, as a commercial product, from the functionality available inside Matlab, Maple, or Mathematica? Those all have the same kind of notebook feature, but have the additional advantage of thousands of third-party libraries.

edit to add:

This project seems to be pretty neat, and it’s clear that a ton of work has gone into it, but I’m unlikely to ever use it.

Here’s my list of criteria for something like this:

(1) Is it open source? Am I being locked into someone’s proprietary environment? Can I inspect the code of every function I’m calling on, to make sure I trust them to behave correctly?

(2) Does it interoperate easily with my existing data and workflows? Can I easily scrape a webpage to feed data in, or import from a file in some obscure format from the 90s?

(3) Can I run it offline? Can I share it with anyone I want, and can they build on what I’ve made without paying a license fee? [Personally I think running on a computer locally is a big advantage over having everything done “in the cloud” and displaying in a web page, and thus being completely unavailable when offline. I’m assuming all the numeric code is being run on some server somewhere? Or is all the processing done locally in Javascript?]

(4) Is there some well tested library that already solves my problem that I can run within the tool, so that I can just download the library, use its API, and be done without a bunch of custom work on my end?

[Or more generally: does the tool solve some problem that I can’t easily solve in any other way?]

(5) Is the plotting functionality easy enough to make plots of data with a few seconds of work, but flexible enough that I can make a custom data visualization if I need to? (For a web project, I would just feed the data to D3.)

Don’t let me discourage you though. It’s great that people are working on tools, and quite possible that you’ll find a good market of folks who would use this thing.