Type annotation on variables in Typescript - Mini Project: Build & Apply

Type annotation on variables

📖 Scenario: You are creating a simple program to store information about a book. You want to make sure the types of the variables are clear and correct.

🎯 Goal: Learn how to add type annotations to variables in TypeScript to make your code safer and easier to understand.

📋 What You'll Learn

Create variables with explicit type annotations

Use string and number types

Assign correct values matching the types

Print the variables to see their values

💡 Why This Matters

🌍 Real World

Type annotations help developers avoid mistakes by clearly stating what kind of data each variable should hold. This is very useful in real projects to prevent bugs.

💼 Career

Many programming jobs require writing clear and safe code. Knowing how to use type annotations in TypeScript is important for frontend and backend development.

1

Create variables with type annotations

Create a variable called title with type string and value "The Great Gatsby". Create a variable called pages with type number and value 180.

Typescript

// Create variables 'title' and 'pages' with type annotations
// Your code here

Need a hint?

Use let variableName: type = value; to add type annotations.

2

Add a boolean variable with type annotation

Add a variable called isAvailable with type boolean and value true.

Typescript

let title: string = "The Great Gatsby";
let pages: number = 180;
// Add variable 'isAvailable' with type 'boolean'
// Your code here

Need a hint?

Boolean variables use the type boolean and values true or false.

3

Change the value of a variable with the correct type

Change the value of pages to 200. Make sure the type annotation stays the same.

Typescript

let title: string = "The Great Gatsby";
let pages: number = 180;
let isAvailable: boolean = true;
// Change the value of 'pages' to 200
// Your code here

Need a hint?

Keep the type annotation : number and update the value after the equals sign.

4

Print all variables to the console

Write three console.log statements to print the values of title, pages, and isAvailable.

Typescript

let title: string = "The Great Gatsby";
let pages: number = 200;
let isAvailable: boolean = true;
// Print the variables below
// Your code here

Need a hint?

Use console.log(variableName); to print each variable.