Folly is more like an addition to the standard library. For that sort of library, you want parts to be deprecated over time as the language's standard library grows. React has no place in a standard library; it's more of a framework.

That you simply ignore the fact that C++ projects generally do prefer to not build from any "framework".

Framework in JS, is just similar to a more abstracted library in C++.

In the whole stack (or spectrum) of machine, language, application, C++'s design philosophy naturally encourage things like Folly and Absl. Just like JS encourages React, VUE etc.

This is more like if every company reimplemented core-js... worth a little more examination than "large companies write libraries"

React attempts the re-implement the browser DOM API and its associated UI conventions. That's way more WTF than folly, which is basically jQuery for C++.

React attempts to wrap the browser DOM API and it's conventions in a way that's (for people who use it) easier to reason about, that's kind of like saying Anvil is a WTF because it wraps Vulcan

Also yeah, every reimplementing jquery would be extremely strange and mostly defeat the point of jquery... which is to not have to implement jquery's constructs in Vanilla JS

I don't think I agree, most don't reinvent the common parts: jQuery, lodash, angular or react

Most don't, but Facebook does have its own equivalent of jQuery, lodash and angular. A few other very large tech companies are similar.

Most C++ shops don't have their own equivalent of Folly, they use Boost or Google's Abseil or something else.

I think that's the key point, the scale in which this starts happening is the sizes of the Googles and Facebooks of the world (in C++: Abseil and Folly) but also in Java (at Google: Guava), JavaScript (at Google: closure, Angular/Polymer/Lit/and many others).

So people extrapolating from a ~100 person company or a ~1000 person company using JS might as well think it's about the language, but it's really about the size, I think.

Closure isn't so much a standard library as a typescript alternative though, I don't think the comparison works.

Look at Google and the Closure standard library for an example of a company writing a lot of JS that ended up writing it's own "standard library"-like thing.