How can I change a readonly property in TypeScript?

Question

I want to be able to make readonly properties (not getters) for users of my class, but I need to update them internally; is there a way to do this and allow to

Answer 1

My current solution for TypeScript 3.6.3

type Mutable = {
   -readonly [k in keyof T]: T[k];
};

class Item {
  readonly id: string;

  changeId(newId: string) {
    const mutableThis = this as Mutable;
    mutableThis.id = newId;
  }
}