Type alias for unions in Typescript - Mini Project: Build & Apply

Type alias for unions

📖 Scenario: You are building a simple program to categorize different types of pets by their names and types.

🎯 Goal: Create a type alias for a union of pet types, use it in a variable, and print the pet's type.

📋 What You'll Learn

Create a type alias called PetType that is a union of the strings 'dog', 'cat', and 'bird'.

Create a variable called myPet with the type PetType and assign it the value 'cat'.

Print the value of myPet.

💡 Why This Matters

🌍 Real World

Type aliases for unions help you restrict variables to specific allowed values, making your code safer and easier to understand.

💼 Career

Many jobs require writing clear and safe TypeScript code, especially when working with APIs or user input where only certain values are valid.

1

Create a type alias for pet types

Create a type alias called PetType that is a union of the strings 'dog', 'cat', and 'bird'.

Typescript

// Your code here

Need a hint?

Use the type keyword followed by the alias name, then assign the union of string literals separated by |.

2

Create a variable with the type alias

Create a variable called myPet with the type PetType and assign it the value 'cat'.

Typescript

type PetType = 'dog' | 'cat' | 'bird';
// Your code here

Need a hint?

Declare myPet with let, specify the type PetType, and assign the string 'cat'.

3

Use the variable in a function

Create a function called describePet that takes a parameter pet of type PetType and returns a string describing the pet type. Then call describePet with myPet and store the result in a variable called description.

Typescript

type PetType = 'dog' | 'cat' | 'bird';

let myPet: PetType = 'cat';
// Your code here

Need a hint?

Define a function with parameter pet of type PetType that returns a string using a template literal.

4

Print the description

Print the value of the variable description using console.log.

Typescript

type PetType = 'dog' | 'cat' | 'bird';

let myPet: PetType = 'cat';

function describePet(pet: PetType): string {
    return `My pet is a ${pet}.`;
}

let description = describePet(myPet);
// Your code here

Need a hint?

Use console.log(description) to print the description.