// There are also 25 objects that // have a private identifier and a method to assign it // as well as a creation date field. // The identifier can contain a number or a string. // The creation field can also contain a string or a number. // The types for creation date and identifier match (either string or number) // Describe the type for such objects let a = { getId: () => createdId: [phone] } let b = { getId: () => 'id', createdAt: '[phone]T20:00:00Z' } // this object SHOULD NOT match the type: let c = { getId: () => 56, createdAt: '[phone]T20:00:00Z' }

To describe such an object in TypeScript, you can use a union of types for the identifier and creation date, and also define a getId method that returns a value of the same type as the createdAt field.

Example of the type:

type IdType = string | number;

interface ObjWithIdAndDate {
  getId: () => IdType;
  createdAt: IdType;
}

Examples of objects matching the type:

const a: ObjWithIdAndDate = {
  getId: () => 123,
  createdAt: 456
};

const b: ObjWithIdAndDate = {
  getId: () => 'id123',
  createdAt: '2023-06-01T20:00:00Z'
};

Object c does not match the type if getId returns a number and createdAt is a string, or vice versa, since the types must match. To check this, you can use generics or perform an additional check, but in a simple case, it is enough to describe the type as above.