How do you emulate ADTs and pattern matching in TypeScript?

Question

Unfortunately, as of 0.9.5, TypeScript doesn\'t (yet) have algebraic data types (union types) and pattern matching (to destructure them). What\'s more, it doesn\'t even supp

Answer 1

To answer

it doesn't even support instanceof on interfaces.

Reason is type erasure. Interfaces are a compile type construct only and don't have any runtime implications. However you can use instanceof on classes e.g. :

class Foo{}
var x = new Foo();
console.log(x instanceof Foo); // true