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Comment by dgb23 | Hacker News Reader

I use recursion in JS when implementing generic trees/dags. I'm not worried at all about growing the stack because I use the language for UI stuff, where the depth of the trees is quite shallow and the data is small overall.

I don't really know what the utility of TCO/proper tail calls would be. You already have UX constraints that nudge to avoid having a ton of stuff on the screen.

As an example of where recursion of generic trees could be applied in a UI: Look at HN threads. Even exceptionally large threads have what, a couple hundred responses? With depth of maybe a dozen? Also you typically have affordances to navigate such a tree and only see the parts of it that you want. So it becomes even more trivially small.

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I ran out of JS stack, walking the dependency graph of a big computation. Dependency graphs can be very deep relative to their overall size. It was a big pain to rewrite with an explicit stack of to-be-visited nodes.

TCO wouldn't have saved me, though. It just needs a big stack. Node defaults to just under 1 MB, which doesn't go very far.

That's interesting and quite valid, haven't thought of this. And I agree, recursion is often more intuitive and concise for these things.

Rewriting a recursive function into a for-loop can be mind boggling, but you often end up with more simple code.

Javascript is also a very popular back-end language (Node JS)..

Yes, but even there it is typically used for stuff that leans towards front-end. People don't typically write databases and messaging systems in Nodejs.

I wonder about specific use cases where stack allocating recursion actually becomes an issue in the JS world.

People do a lot more in JavaScript than you realize.

That's what I'm wondering about. When was the last time you blew the stack with JS and what did you try to accomplish?

Another commenter said they had problems walking a dependency graph.

For some examples: People have 3D game engines running in JavaScript. There's a lot of cryptographic work in JavaScript, including but not limited to cryptocurrencies - a lot of groundbreaking stuff from a technological perspective. Full blown emulators, developer tools, virtual machines... the world of JavaScript is way larger than CRUD applications.

> I don't really know what the utility of TCO/proper tail calls would be. You already have UX constraints that nudge to avoid having a ton of stuff on the screen.

The only thing you can think of using recursion for is walking the DOM?

Not specifically walking the DOM but doing DOM/UI related stuff with JS is where I sometimes use recursion. This might also be data processing, but that data is often small and shallow enough for stack growth not not matter, because it is typically related to the UI in _some_ way.

I don't typically use JS for heavy computation of large datasets that lend themselves to recursion. The only thing I can think of that is somewhat large is data visualizations and drawing graphs interactively, but there you typically have a matrix or just a flat array.

Would be nice to be able process huge arrays recursively.

The utility would be in the computational space, particularly when solving a problem functionally.

Yes absolutely. After learning about problem solving through recursive algorithms (SICP/HTDP) I was quite sad to find that JavaScript/TypeScript didn't have this.

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