Explicit type annotations in Typescript - Mini Project: Build & Apply

Explicit type annotations

📖 Scenario: You are creating a simple program to store and display information about a book in a library system.

🎯 Goal: Learn how to use explicit type annotations in TypeScript to define the types of variables and function parameters.

📋 What You'll Learn

Create variables with explicit type annotations

Define a function with typed parameters and return type

Use the variables and function to display information

💡 Why This Matters

🌍 Real World

Explicit type annotations help developers understand what kind of data variables and functions expect, reducing bugs in real-world applications like library systems.

💼 Career

Many programming jobs require writing clear, typed code to maintain large codebases and collaborate with teams effectively.

1

Create variables with explicit type annotations

Create a variable called title with type string and value "The Great Gatsby". Create a variable called year with type number and value 1925.

Typescript

# Create a variable called title with type string and value "The Great Gatsby"
# Create a variable called year with type number and value 1925

Need a hint?

Use let variableName: type = value; to declare variables with explicit types.

2

Add a variable with explicit boolean type

Create a variable called available with type boolean and value true.

Typescript

let title: string = "The Great Gatsby";
let year: number = 1925;
# Create a variable called available with type boolean and value true

Need a hint?

Boolean variables can be declared with type boolean and values true or false.

3

Create a function with typed parameters and return type

Create a function called getBookInfo that takes parameters title (type string), year (type number), and available (type boolean). The function should return a string combining these values in the format: "Title (Year) - Available" or "Title (Year) - Not Available" depending on the available value.

Typescript

let title: string = "The Great Gatsby";
let year: number = 1925;
let available: boolean = true;
# Create function getBookInfo with typed parameters and return type string

Need a hint?

Use function functionName(param: type, ...): returnType { ... } to define typed functions.

4

Display the book information using the function

Use console.log to print the result of calling getBookInfo with the variables title, year, and available.

Typescript

let title: string = "The Great Gatsby";
let year: number = 1925;
let available: boolean = true;

function getBookInfo(title: string, year: number, available: boolean): string {
    return `${title} (${year}) - ${available ? "Available" : "Not Available"}`;
}

# Print the book information using console.log and getBookInfo

Need a hint?

Call the function with the variables and print the result using console.log.