What is the approach for mapping an object with nested objects/types in Typescript?

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The approach for mapping an object with nested objects/types in Typescript involves recursively iterating through the object's properties and mapping any nested objects/types as well. This can be accomplished using a combination of interfaces, classes, and helper functions.

1. Define the interface for the object being mapped, including any nested object/types.

interface Person {
  name: string;
  age: number;
  address: {
    street: string;
    city: string;
    state: string;
  };
}

1. Create a class that implements the interface and provides a method for mapping the object.

class PersonModel implements Person {
  name: string;
  age: number;
  address: {
    street: string;
    city: string;
    state: string;
  };

  constructor(person: Person) {
    this.name = person.name;
    this.age = person.age;
    this.address = person.address ? new AddressModel(person.address) : null;
  }

  toJson(): object {
    return {
      name: this.name,
      age: this.age,
      address: this.address ? this.address.toJson() : null,
    };
  }
}

1. Create a similar class for any nested objects/types, and use the constructor to recursively map the object.

class AddressModel implements Address {
  street: string;
  city: string;
  state: string;

  constructor(address: Address) {
    this.street = address.street;
    this.city = address.city;
    this.state = address.state;
  }

  toJson(): object {
    return {
      street: this.street,
      city: this.city,
      state: this.state,
    };
  }
}

1. Use a helper function or library to instantiate the top-level class and map the object.

function mapPerson(person: Person): object {
  const personModel = new PersonModel(person);
  return personModel.toJson();
}