AgentSkillsCN

type-vs-interface

在 TypeScript 中，所有类型声明均采用 type 而非 interface（作为项目标准）。

SKILL.md
--- frontmatter
name: type-vs-interface
description: Use type instead of interface for all type declarations in TypeScript (project standard).

Use type (Not interface)

Rule

Always use type for type declarations. Never use interface.

✅ Good (type)

typescript
type User = {
  name: string;
  email: string;
};

type Settings = {
  theme: "light" | "dark";
  language: string;
};

❌ Bad (interface)

typescript
interface User {
  name: string;
  email: string;
}

Why?

  • •Project standard for consistency
  • •type is more flexible (unions, intersections, primitives)
  • •Simpler mental model (one way to declare types)

What type Can Do That interface Can't

Union Types

typescript
type Status = "idle" | "loading" | "success" | "error";

Intersection Types

typescript
type Admin = User & { role: "admin" };

Primitive Aliases

typescript
type ID = string | number;

Mapped Types

typescript
type Readonly<T> = { readonly [K in keyof T]: T[K] };

When Refactoring

Search and replace all interface declarations with type:

bash
# Find interfaces
grep -r "^interface " src/