This article provides good insight on the boom, but leaves out any insight on the inevitable bust - not on JS per se, but the distinct runtimes.

Deno and Bun seem to be two highly competitive runtimes, each VC backed and positioned against each other, but the fairly tale of multiple winners seems unlikely in a world that favors power laws.

So then, how do others see these ecosystems surviving over the next decade? What are the canaries? And, how interoperable will our code be?

WinterCG is trying to help standardize web APIs to address these concerns. So one strategy when writing server-side js is to stick to standard APIs as much as possible.

If you do want to leverage runtime-specific code you can isolate that code in separate modules, so if you ever do need to migrate off a particular runtime it's easier to identify/replace that code.

Ultimately it's all JavaScript, and since most of these runtimes are open source even if they're abandoned we might see community forks. Though even if your chosen runtime is completely without support, I don't see a migration off being an extremely urgent or difficult task for most projects.

A very good thought! Deno and Bun have this formidable funding for sure, but Node.js is still innovating. Things like type-stripping and require(esm) come to mind. I think as long as big companies use it for Electron, Node.js will continue to get investment. Even if the investment were to dry up, experience teaches us that old tools die hard.

I would hope that interoperability goes up. The React Native community are closing in on support for Node-API, and with that maybe we can start sharing native code between desktop and mobile. The WinterCG effort is also going well.

As for canaries, I think sustainability is the main thing to look at. What is the surface area of this tool, how much expertise and effort does it take to maintain it, and who is invested in its survival? The more we can share common implementations like Intl and Temporal, the easier it is for smaller players to keep up. And of course, the more the big players try to diverge (looking at you, Chrome), the harder it gets.