Well, you are likely taking examples from library internals.
Libraries exist, in part, to encapsulate high complexity.
There's likely accompanying documentation for the examples you provided.
In some other languages you have similar stuff, with the added complexity of concurrency and memory management related types. If you are struggling with TypeScript, let me tell you about a whole new world of pain called C++.
That's why I think every programmer should learn C++.
Libraries exist, in part, to encapsulate high complexity.
There's likely accompanying documentation for the examples you provided.
In some other languages you have similar stuff, with the added complexity of concurrency and memory management related types. If you are struggling with TypeScript, let me tell you about a whole new world of pain called C++.
That's why I think every programmer should learn C++.