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TypeScript Styleguide

Interface vs Type for Object Definitions

Two ways to define object types in TypeScript. Explore the differences between interfaces and type aliases for type definitions.

79%

Use Interface

21%

Use Type Alias

Interface

TypeScript's dedicated keyword for object contracts with structural subtyping support.

Code Example

example.ts (interface)
interface User {
  id: number;
  name: string;
  email: string;
}

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

Key Benefits

  • Designed specifically for object shapes
  • Supports declaration merging
  • Better for public APIs
  • Clearer intent for object contracts
  • Supports 'extends' inheritance
  • Structural typing built-in

Statistics

Type Alias

Flexible type aliases that can represent any type, including objects, unions, and tuples.

Code Example

example.ts (type)
type User = {
  id: number;
  name: string;
  email: string;
};

type Admin = User & {
  role: 'admin';
  permissions: string[];
};

Key Benefits

  • Works with any type, not just objects
  • Supports union and intersection types
  • More flexible for complex types
  • Consistent with other type definitions
  • No declaration merging
  • Modern alternative to interfaces

Statistics

Additional Insights

More data points to help you make an informed decision for your team.

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