TypeScript — Namespaces

Basic namespace

namespace Validation {
  export interface Validator {
    validate(value: string): boolean;
  }

  export class EmailValidator implements Validator {
    validate(value: string): boolean {
      return /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(value);
    }
  }
}

const validator = new Validation.EmailValidator();

Nested namespaces

namespace Shapes {
  export namespace Polygons {
    export class Triangle {}
    export class Square {}
  }
}

const triangle = new Shapes.Polygons.Triangle();

Aliases

import ShapeValidator = Validation.ShapeValidator;

When to use

• Legacy codebases
• Avoiding global pollution
• Library organization

Modern alternative

// Prefer modules over namespaces
// modules/user.ts
export interface User {
  name: string;
}

// index.ts
import { User } from './modules/user';

Mini Practice

1. Create namespace
2. Export from namespace
3. Use nested namespaces
4. Compare with modules

Up Next

Continue with Ambient Declarations - Type declarations.