I know it's not a new concept, but it's just not the way traditional software is developed. Tradition software is usually done in the complete antithesis to the way a REPL environment works.

I guess that's the main reason why so many software developers don't "get" why people want to write code in a browser. Even normal Python developers.

I'm a REPL-first obstinate Lisper and a recent fan of Observable Notebooks, and I still don't like writing code in the browser. The browser is an excellent rendering engine, but absolutely sucks at typing & developer conveniences. If someone could make a cross between Emacs and Chrome (preferably with elisp instead of JS), I'd be in heaven.

It is called Visual Studio Code. Switched from emacs and haven’t looked back so far.

I don't "get" why people want to write code in a browser NOT because I find REPL useless but because I find browser a poor choice of program to input code. I use REPL all the time, but I use emacs to do this. My firefox isn't customized to type code, it's customized to type HN comments and watch cat videos. Why use firefox instead of emacs to type code?

In my view, Jupyter Notebooks are web-based because they are designed with sharing in mind. It's far from perfect (git does not play nicely with .ipynb files :(), but here are two specific advantages that come to mind:

- You can run a Jupyter Notebook locally or on a remote server, seamlessly working in a graphics- and Markdown-capable REPL in either case

- You can easily share and export the final notebook in its post-run state, presenting Markdown, LaTeX formulas, code, comments, plots, and results in the order they were written and executed, in a single (HTML or PDF) document (or even a slide deck, if you dare)

To your last point about limiting use of the browser to writing short comments and watching videos: I'd say that's a matter of personal taste. Browsers are perfectly capable of quickly handling the volume of code and text that would appear in a reasonable notebook.

That said, I grew up with vim keybindings, and while Jupyter supports the basics (modal editing, j and k to move between cells, dd to delete a cell, etc.) and has super useful default keyboard shortcuts, I still move and type faster in vim. But Jupyter adds so much value as a seamless, graphics-enabled, run-anywhere REPL that I happily accept the slight slowdown in my typing and navigation, which is never the bottleneck in my R&D work anyway.

You can replace "firefox" and "emacs" with other things to take that last argument to an extreme. For example: "My [laptop] isn't customized to type code, it's customized to type HN comments and watch cat videos. Why use [a laptop] instead of [a workstation] to type code?" I thought like that 15 years ago, but technology and I changed.

It's not about performance. I have no problem with jupyter notebook. I use ein-mode in emacs which is basically a better frontend for jupyter notebook AND you get all benefits of emacs since cells are individual emacs buffers. It's also not about browsers. Writing code in a medium that's not designed to write code encourages bad behavior. Jupyter notebook is supposed to be optimized for Julia, Python and R but somehow writing Python code is next to impossible because it doesn't understand what to do with indentation. There is almost no word suggestion, when I type a few characters and click tab I almost always get horrible suggestion and have to navigate with arrow keys. I cannot use C-q to comment stuff out/in intelligently (comment-dwim), I cannot use regex, I cannot fuzzy search, I cannot use multiple cursors, I cannot use replace-text, I cannot highlight SQL embedded in python. I can go on for days. And this is not a problem of jupyter notebook. Why reinvent the wheel? We already have text editors and IDEs that solve the problem of inputing code, why would you ever want to type code in a web input box? That is, unless someone spends more money and makes a full-fledged IDE in local javascript. So much wasted effort for a problem that was solved in 1960s.