Type vs. Interface in TypeScript: What's the Difference?
Hey everyone!
Lately, I've been digging deeper into TypeScript, and I thought I'd share some insights on a topic that often confuses many of us: the difference between type
and interface
. If you've ever wondered when to use one over the other, you're not alone!
🔍 So, what's the deal?
Both type
and interface
allow us to define custom types in TypeScript, but they have their own unique features and use cases. Here's a breakdown:
📝 Type Aliases (type
)
What are they?
- Think of
type
as a way to give a name to any type. This could be a primitive, a union, a tuple, an object, or even a function type.
Pros:
- Versatility with Complex Types: Perfect for defining unions and intersections.
type Status = "success" | "error" | "loading";
- Primitives and Tuples: You can alias primitive types, tuples, and more.
type Point = [number, number];
- Advanced Type Features: Great for mapped types and conditional types.
Cons:
- No Declaration Merging: Unlike interfaces, you can't reopen a type alias and add new properties later.
- Less OOP-Friendly: Types can't be implemented by classes or extended in the same way interfaces can.
📐 Interfaces (interface
)
What are they?
- Interfaces are primarily used to describe the shape of objects, including their properties and methods.
Pros:
- Extensibility: You can extend interfaces or even merge them. This is super handy for large codebases.
interface User {
name: string;
}
interface User {
age: number;
}
// User now has both name and age properties
- Class Implementation: Ideal for object-oriented patterns. Classes can implement interfaces.
interface Drivable {
drive(): void;
}
class Car implements Drivable {
drive() {
// implementation
}
}
Cons:
- No Union Types: Interfaces can't define union types directly.
- Limited with Primitives and Tuples: Not suitable for aliasing these types.
🤔 So, which one should you use?
Use type
when:
- Defining complex types like unions and intersections.
- Working with primitives, tuples, or function types.
- You need advanced type manipulation.
Use interface
when:
- Defining the shape of an object or class.
- You might need to extend or merge types later on.
- Following object-oriented design patterns.
💡 My Two Cents
Personally, I lean towards using interface
for defining objects and classes because I appreciate the extensibility. For everything else, especially when dealing with unions or more complex types, type
is my go-to.
But that's just me! What's your experience? Do you have a preference between type
and interface
in TypeScript? I'd love to hear your thoughts and any tips you might have.
Feel free to share in the comments below! 👇
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