Typescript Exercises 2

Typescript Exercise 2

Exercise 2

Type Person is missing, please define it and use it in persons array and logPerson function in order to fix all the TS errors.

interface User {
  name: string;
  age: number;
  occupation: string;
}

interface Admin {
  name: string;
  age: number;
  role: string;
}

export type Person = unknown;

export const persons: User[] /* <- Person[] */ = [
  {
    name: 'Max Mustermann',
    age: 25,
    occupation: 'Chimney sweep',
  },
  {
    name: 'Jane Doe',
    age: 32,
    role: 'Administrator',
  },
  {
    name: 'Kate Müller',
    age: 23,
    occupation: 'Astronaut',
  },
  {
    name: 'Bruce Willis',
    age: 64,
    role: 'World saver',
  },
];

export function logPerson(user: User) {
  console.log(` - ${user.name}, ${user.age}`);
}

persons.forEach(logPerson);

How I Solved This Problem

Variable persons is Array of Objects and it is considered as User[] type.

However, Each object contains different properties like role and occupation

while property role belongs to User type, property occupation belongs to type Admin.

By using Union Type, typescript can choose what properties persons contained object has.

interface User {
  name: string;
  age: number;
  occupation: string;
}

interface Admin {
  name: string;
  age: number;
  role: string;
}

export type Person = User | Admin;

export const persons: Person[] /* <- Person[] */ = [
  {
    name: 'Max Mustermann',
    age: 25,
    occupation: 'Chimney sweep',
  },
  {
    name: 'Jane Doe',
    age: 32,
    role: 'Administrator',
  },
  {
    name: 'Kate Müller',
    age: 23,
    occupation: 'Astronaut',
  },
  {
    name: 'Bruce Willis',
    age: 64,
    role: 'World saver',
  },
];

export function logPerson(user: Person) {
  console.log(` - ${user.name}, ${user.age}`);
}

persons.forEach(logPerson);