I think it’s a +1 to using both depending on where they fit. I use type aliases for defining unions and intersections and such and interfaces for everything else, personally.
And that’s an intersection you’re describing there, not a union. Interfaces are explicit about extension as well, they use the “extends” keyword.
Whoops, yes that is indeed a union not an intersection. Thanks for the correction. I'm still getting used to the terminology.
The explicitness I was referencing is around the declaration merging. Its automatic so unless there's a conflict between two interfaces with the same name but with different properties, a dev wouldn't know that it was being done.
I agree with using what makes sense for the scenario. I prefer type aliases for functions and interfaces for classes and that seems to work out pretty well so far.
The fact that interfaces are limited to typing objects but type aliases can also be used for functions is an easy +1 to type aliases.
My view is that declaration merging is a bit of an anti pattern that could cause trouble if two different people write an interface with the same name but to represent different data... now they get merged incorrectly. A type alias forces more explicit behavior where composition must be done by creating a new type alias as the union of two or more other types
Edit: found the page, its here https://www.typescriptlang.org/docs/handbook/advanced-types....Yeah, not sure I agree yet but I could be persuaded... I don't think type aliases prevent extension, they just force it to be explicitly declared.