Demystifying TypeScript: Choosing Between Interfaces and Types for Stronger Code Structures

In the TypeScript universe, the ‘interface’ and ‘type’ declarations are akin to superheroes for shaping our data structures. But, when should we call on ‘interface,’ and when does ‘type’ swoop in to save the day? In this concise guide, we’ll unravel the mystery, exploring the differences and use cases of these two constructs. By the end, you’ll have a clear roadmap for crafting robust TypeScript code. Let’s dive in!

Interfaces:

Declaration:

• Interfaces are often used to define contracts for object shapes.
• They can be extended and merged to create more complex interfaces.

interface Person {
  name: string;
  age: number;
}

Compatibility:

• Interfaces support declaration merging, allowing you to extend an existing interface declaration.

interface Person {
  gender: string;
}

Extending:

• Interfaces can extend other interfaces, promoting code reusability.

interface Employee extends Person {
  employeeId: string;
}

Declaration Merging:

• Multiple interface declarations with the same name are automatically merged.

interface Car {
  brand: string;
}

interface Car {
  model: string;
}

Types:

Declaration:

• Types are versatile and can be used to define not only object shapes but also union types, intersections, and more.

type Person = {
  name: string;
  age: number;
};

Compatibility:

• Types can be used with primitive types, unions, intersections, and more, offering greater flexibility in type definitions.

type Gender = 'male' | 'female';

type Person = {
  name: string;
  age: number;
  gender: Gender;
};

Extending:

• While types can’t extend like interfaces, they can be combined using union and intersection types.

type Employee = Person & {
  employeeId: string;
};

Utility Types:

• TypeScript provides utility types like Partial, Readonly, and Pick that work seamlessly with types.

type PartialPerson = Partial<Person>;
type ReadonlyPerson = Readonly<Person>;
type PickName = Pick<Person, 'name'>;

When to Use Which?

Use Interfaces When:

• Defining contracts for object shapes.
• Extending or merging declarations.
• Interacting with code that relies heavily on interfaces (e.g., third-party libraries).

Use Types When:

• Defining more complex types, unions, and intersections.
• Working with primitive types, literals, and mapped types.
• Taking advantage of utility types provided by TypeScript.

In many scenarios, interface and type can be used interchangeably, and the choice between them often comes down to personal preference or specific use cases. It's worth noting that TypeScript evolves, and future updates may introduce new features or refine existing ones.

Now armed with this knowledge, go forth and wield ‘interface’ and ‘type’ judiciously, sculpting your data structures with finesse in the TypeScript world. Happy coding!❤️