array.ts

class A {
	public a() {
		alert("A!");
	}
}
class B extends A {
	public b() {
		alert("B!");
	}
}

var bs: B[] = [new B(), new B()];
var as: A[] = bs;
as[1] = new A();
as.forEach(a => a.a());
bs.forEach(b => b.b());