readonly-properties-in-typescript.ts

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interface House {
  readonly ownersName: string;
  readonly address: {
    readonly line1: string;
    line2?: string;
    readonly postCode: string;
  };
}

const house: House = {
  ownersName: "Foo Bar",
  address: {
    line1: "Baz Qux",
    postCode: "102030",
  },
};

house.ownersName = "Foo";

house.address.line1 = "Bar";

house.address.line2 = "Baz";