In TypeScript, both interfaces and type aliases are powerful constructs that allow you to define the shape of data. The choice between using an interface or a type alias often depends on the specific requirements of your code as well as personal or team preferences. However, there are some key differences and use cases for each that can help guide your decision.
Interfaces
Interfaces in TypeScript are used to define the shape of an object. They can declare properties, methods, and events that an object must implement. Interfaces are particularly useful when you need to define a contract for classes, ensuring that they implement specific properties and methods. One of the most significant features of interfaces is their ability to be extended and implemented by classes, making them ideal for defining complex object structures and for use in object-oriented programming patterns.
Open-ended: Interfaces are open-ended, meaning you can extend an existing interface by declaring it a second time with new or overridden properties. This feature is particularly useful for augmenting existing types or interfaces from third-party libraries without modifying the original source code.
Extensibility: Interfaces can extend other interfaces, allowing you to create a hierarchy of more specific interfaces from a general base interface.
Implementation: Classes can implement interfaces to ensure they adhere to a specific contract, making interfaces a key part of TypeScript's support for object-oriented principles.
Type Aliases
Type aliases, on the other hand, are a way to give a type a new name. They can be used to simplify complex type annotations, create unions, intersections, and more. Type aliases are versatile and can represent not only object shapes but also unions, primitives, tuples, and any other types.
Flexibility: Type aliases are more flexible than interfaces. They can describe not just the shape of objects but also unions, primitives, and tuples. This makes type aliases suitable for a wide range of type definitions that interfaces cannot express.
