How TypeScript infers types automatically - Try It Yourself

How TypeScript infers types automatically

📖 Scenario: Imagine you are creating a small program to store information about a book. You want to see how TypeScript can guess the types of your variables without you telling it explicitly.

🎯 Goal: You will create variables with values and see how TypeScript automatically understands their types. Then you will write code that uses these variables, relying on TypeScript's type inference.

📋 What You'll Learn

Create variables with initial values without specifying types

Create a helper variable to hold a count

Use a function that uses the inferred types

Print the results to the console

💡 Why This Matters

🌍 Real World

When writing code, TypeScript helps by guessing types so you write less code and avoid mistakes.

💼 Career

Understanding type inference is important for working efficiently with TypeScript in real projects, improving code quality and developer productivity.

1

Create variables with initial values

Create a variable called title and set it to the string "The Great Gatsby". Then create a variable called pages and set it to the number 180.

Typescript

// Your code here

Need a hint?

TypeScript will guess that title is a string and pages is a number because of the values you assign.

2

Add a helper variable

Create a variable called copiesSold and set it to the number 5000.

Typescript

let title = "The Great Gatsby";
let pages = 180;
// Your code here

Need a hint?

This variable will also have its type inferred as a number.

3

Use a function with inferred types

Create a function called getBookSummary that takes no parameters and returns a string combining title and pages in this format: "The Great Gatsby has 180 pages.". Use the variables title and pages inside the function.

Typescript

let title = "The Great Gatsby";
let pages = 180;
let copiesSold = 5000;
// Your code here

Need a hint?

TypeScript knows title is a string and pages is a number, so you can use them directly in the template string.

4

Print the result

Write a console.log statement to print the result of calling getBookSummary().

Typescript

let title = "The Great Gatsby";
let pages = 180;
let copiesSold = 5000;

function getBookSummary(): string {
    return `${title} has ${pages} pages.`;
}
// Your code here

Need a hint?

This will show the combined string in the console, demonstrating how TypeScript inferred the types correctly.