Typescript Exercises 3

Typescript Exercise 3

Exercise 3

Fix type errors in logPerson function.
logPerson function should accept both User and Admin and should output relevant information according to the
input: occupation for User and role for Admin.

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[] = [
  {
    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(person: Person) {
  let additionalInformation: string;
  if (person.role) {
    additionalInformation = person.role;
  } else {
    additionalInformation = person.occupation;
  }
  console.log(` - ${person.name}, ${person.age}, ${additionalInformation}`);
}

persons.forEach(logPerson);

How I Solved This Problem

We are facing Type Error which is saying property role does not exist on type Person

Since passed parameter person might not have property role,

given condition person.role === true does not always make sense.

if (person.role) {
  additionalInformation = person.role;
} else {
  additionalInformation = person.occupation;
}

Rather than using dot notation to access an object passed as a parameter, it is recommended to use the in operator to check if a property exists in the object, ensuring that the condition is true.

like below

if ('role' in person) {
  additionalInformation = person.role;
} else {
  additionalInformation = person.occupation;
}