Augmenting third-party libraries in Typescript - Mini Project: Build & Apply

Augmenting Third-Party Libraries in TypeScript

📖 Scenario: You are using a popular third-party library that provides a User interface. You want to add a new property to this interface without modifying the original library code.

🎯 Goal: Learn how to safely add new properties to existing third-party interfaces using TypeScript declaration merging.

📋 What You'll Learn

Create an interface augmentation for the third-party User interface

Add a new property isAdmin of type boolean

Create a variable of type User including the new property

Print the new property value

💡 Why This Matters

🌍 Real World

Many libraries provide interfaces you cannot change directly. Augmenting lets you add your own properties safely.

💼 Career

Understanding how to extend third-party types is important for working with large codebases and popular libraries in TypeScript.

1

Create the original User interface

Create an interface called User with properties name (string) and email (string).

Typescript

# Your code here

Need a hint?

Use interface User { name: string; email: string; } to define the interface.

2

Augment the User interface with isAdmin

Add a new property isAdmin of type boolean to the existing User interface using declaration merging.

Typescript

interface User {
  isAdmin: boolean;
  // Your code here
}

Need a hint?

Write interface User { isAdmin: boolean; } separately to add the new property.

3

Create a User object including isAdmin

Create a variable called user of type User with name set to "Alice", email set to "[e-mail]", and isAdmin set to true.

Typescript

// Create the user object here
// Your code here

Need a hint?

Use const user: User = { name: "Alice", email: "[e-mail]", isAdmin: true };.

4

Print the isAdmin property

Write a console.log statement to print the value of user.isAdmin.

Typescript

// Print the isAdmin property
// Your code here

Need a hint?

Use console.log(user.isAdmin); to print the value.