It's not a cryptographic key or a secret of any kind. In the case of React (or other JS libraries) export identifiers are chosen to expose private APIs for integration purposes with things like developer tooling and other functionality that isn't part of the publicly documented API.

Instead of choosing something like `__PRIVATE` the React library in particular chose something more eye catching: `__SECRET_INTERNALS_DO_NOT_USE_OR_YOU_WILL_BE_FIRED`, which is definitely sure to get people's attention when they look into it, but is essentially just a joke.

Because there are some really terrible projects out there made by guys who think that a two week "bootcamp" is enough to make you a competent developer. An SPA needs to access a third party resource of some sort (in my case it was Power BI), and fetching the necessary authentication information from your server with proper authorization is apparently too complicated. I ain't rewriting that shit, I have too much work already.

Not a crypto key (I hope). In JS, objects (dictionaries) are key-value pairs.

I meant... a property name. Like `{ [key]: value }`