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interface

class

Defines the shape of an object. Supports optional properties (?), readonly, and extension (extends).

Syntax

interface Name { property: type; method(): returnType; }

Example

javascript

interface User {
    id: number;
    name: string;
    email: string;
    age?: number;          // optional
    readonly createdAt: Date; // immutable
}

interface Admin extends User {
    role: 'admin' | 'superadmin';
    permissions: string[];
}

const user: User = {
    id: 1,
    name: 'Alice',
    email: 'alice@example.com',
    createdAt: new Date(),
};

any / unknown / never / void

type alias