Type Aliases for Objects

Part of the Introduction To TypeScript section of Coddy's JavaScript journey — lesson 38 of 73.

TypeScript allows you to create a type alias that defines a reusable shape for objects.

A type alias uses the type keyword to create a named definition for an object structure. Once defined, you can use this alias anywhere you need that specific object shape:

type Product = {
  name: string;
  price: number;
  inStock: boolean;
};

let laptop: Product = {
  name: "Gaming Laptop",
  price: 1299,
  inStock: true
};

let phone: Product = {
  name: "Smartphone",
  price: 699,
  inStock: false
};

Challenge

Easy

Create a type alias named Book for an object with the following properties:

title of type string
author of type string
pages of type number
isAvailable of type boolean

Create a type alias named Movie for an object with the following properties:

title of type string
director of type string
duration of type number
rating of type string

Using your type aliases, create the following variables:

Create a variable named novel of type Book with title "The Great Gatsby", author "F. Scott Fitzgerald", pages 180, and isAvailable true
Create a variable named textbook of type Book with title "TypeScript Handbook", author "Microsoft", pages 450, and isAvailable false
Create a variable named film of type Movie with title "Inception", director "Christopher Nolan", duration 148, and rating "PG-13"

Create a function named getBookInfo that accepts a parameter of type Book and returns a string in the format "[title] by [author] - [pages] pages".

Create a function named getMovieInfo that accepts a parameter of type Movie and returns a string in the format "[title] directed by [director] ([duration] min)".

Print the following outputs on separate lines:

Call getBookInfo with novel and print the result
Call getBookInfo with textbook and print the result
Call getMovieInfo with film and print the result
Print the availability status of novel (the isAvailable property)

Try it yourself

// TODO: Write your code here

// Create type aliases for Book and Movie


// Create variables using the type aliases


// Create functions to get information


// Print the required outputs

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

Type Aliases for Objects

All lessons in Introduction To TypeScript