Slack allows my colleagues to chock it full of multi-megabyte animated gifs and cat images, but VSCode so far doesn't.

I'm not surprised that Slack's memory use tends to explode.

Yeah I've also tried to understand this. Tried looking for blog posts on what VS Code is doing but couldn't find one. Can someone point out if there's any?

One thing is that they rely on DOM reflow - the automatic, dynamic sizing of elements - as little as possible: nearly everything in the VSCode UI has a fixed size and position. Reflow is arguably the most costly feature of the web when it comes to dynamic apps (though also one of its most valuable features).

Delay loading everything until needed

Parts are written in C/++ no?

Nope.

The file search uses `ripgrep` which is written in Rust. But that is it as far as I know.

Slack is a messy one page app developed by PHP programmers and vscode is open source and actually made by competent people.

Slack is really weird. It seems like they would have the resources to do native applications. I can't fault anyone for doing an Electron app as a demo, prototype, MVP, that's seems completely reasonable.

What I don't get is why they don't want to make a native macOS client, or Windows client. For Linux I get that they don't necessarily know if it should be GTK, QT, should they adopt KDE standards or Gnome, something else maybe? I can see why they would like Electron in that case.

For something like the Mac... They could do a fantastic client, it would use very little memory, play nice with the OS and be fast. Their users would notice and love it.

They have to build and maintain the web version regardless. Why also write individual clients for Windows, Mac and Linux when they can simply wrap the website in a thin desktop wrapper and call it a day?

Because they care about the user experience and delivering the best possible product to their customers? Maybe not.

Based on their success, that's exactly what they are already doing, presumably thanks to the choices they are making.

Maybe it's easy to sell the "One codebase on all platform" idea to the managers and hard to justify the need for high quality app? People are using it anyway.

Especially considering they already have a good iOS Client with their iPad app!

People could perhaps already use that on the M1 Macs and have a better experience.

And I suppose Facebook is therefore also developed by incompetent PHP programmers despite being one of the largest technology companies in the world?

Yes. I am not even joking. Facebook was so terrible that they had to literally reinvent their wheels (hiphop). Its not hard to become a large company when you have black budget backing as confirmed by Snowden.

Your own sentence argues against itself: the team that built HHVM certainly are not "terrible PHP developers"...

You don't think its strange that facebook hired PHP programmers to create the product and then have to hire competent people to fix that shit as far removed from company logic as possible?

Doesn't it kinda make you think, just a little?

I hope you are joking. Those people you call incompetent built arguably the best web application in the world propelling itself into a global corporate juggernaut and that qualifies as built by incompetent people?

The hubris is frightening.