How to check if an object is a readonly array in TypeScript?

Question

How to do an array check (like Array.isArray()) with a readonly array (ReadonlyArray)?

As an example:

Answer 1

Here's relevant issue in typescript.

Suggested workaround by @jcalz is adding overload to declaration of isArray:

declare global {
    interface ArrayConstructor {
        isArray(arg: ReadonlyArray | any): arg is ReadonlyArray
    }
}