When use a interface or class in Typescript [duplicate]

At it's most basic, a class is essentially an object factory (ie. a blueprint of what an object is supposed to look like and then implemented), whereas an interface is a structure used solely for type-checking.

While a class may have initialized properties and methods to help create objects, an interface essentially defines the properties and type an object can have.

In the scenario you described, one would use the interface to set the type for UserLogin.

If you just need to declare a custom type then use interfaces. IMO, there is a very pragmatic reason - they don't get transpiled into JavaScript so the generated code is shorter.

Interfaces won't work if you need to instantiate objects with constructors or use a framework that instantiates and inject them. Then use classes or abstract classes.

Actually both will do the job. I would suggest you to use interfaces though if you just do type-checking as it is specifically designed for that purpose.

Classes and interfaces are powerful structures that facilitate not just object-oriented programming but also type-checking in TypeScript. A class is a blueprint from which we can create objects that share the same configuration - properties and methods. An interface is a group of related properties and methods that describe an object, but neither provides implementation nor initialisation for them.

From: https://toddmotto.com/classes-vs-interfaces-in-typescript