Types & Interfaces

TypeScript provides several basic types: string, number, boolean, array, tuple, enum, any, void, null, undefined.

Interfaces define the shape of an object.

Syntax

TYPESCRIPT

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interface User {
    name: string;
    age: number;
    email?: string;
}

const user: User = {
    name: "John",
    age: 30
};

Interfaces and Type Annotations

TYPESCRIPT

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interface User {
    id: number;
    name: string;
    email: string;
    age?: number;
}

const user: User = {
    id: 1,
    name: "Alice",
    email: "alice@example.com"
};

function showUser(u: User): void {
    console.log(`${u.name} (${u.email})`);
}

showUser(user);

Try It Yourself

Practice

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Exercise

Create an interface for a Product with name and price.

Answer

interface Product {
    name: string;
    price: number;
}

Quick Quiz

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Which keyword defines an interface in TypeScript?

class

type

interface

struct

The "interface" keyword defines the shape of an object in TypeScript.

Retry Quiz

Interview Questions

What is the difference between type and interface?

Both define types, but interfaces can be extended and implemented. Types are more flexible for unions and intersections.

Tutorial Complete

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