3 of those 4 examples wouldn't exist in a statically-typed language like TypeScript

JavaScript had to implement these checks because you could pass a function literally anything and it was on the implementation to deal with it. Typescript has this same problem tbh.

I agree with the spirit of this, but I’d go one more step with the example:

export function clamp(value: number, min: number, max: number): number { return }

That is just adding an extra jump and entry on the callstack where you could just have done:

Math.min(Math.max(value, min), max);

Where you need it.

(The example used was probably just for illustration though)

How are the download rates of these things so high?

Are there 1000 people running 100 CI pipelines/day where downloads aren’t cached?

This is why every language needs a good standard library, which unfortunately JavaScript never had.