class Base {
static f(){console.log('Base')}
}
class A extends Base {
static f(){console.log('A')}
}
class B extends Base {
static f(){console.log('B')}
}
let obj: A|B = new A()
obj.<what to put here>.f()
I don't know the exact class for obj, I need to print A or just call f() for correct class of obj.
I don't need just the class name, that is for example. I am doing more complex things.
prototype, typeof, constructor all seem to be syntax errors.
Both Object.getPrototypeOf() (replacement to the now deprecated Object.prototype.__proto__) or Object.prototype.constructor should work:
Object.getPrototypeOf(obj).constructor.f();
obj.constructor.f();
Actually:
Object.getPrototypeOf(obj).constructor === obj.constructor; // true
Here you can see the compiled source in action:
class Base {
static f() { console.log('Base'); }
}
class A extends Base {
static f() { console.log('A'); }
}
class B extends Base {
static f() { console.log('B'); }
}
const objBase = new Base();
const objA = new A();
const objB = new B();
Object.getPrototypeOf(objBase).constructor.f();
objBase.constructor.f();
Object.getPrototypeOf(objA).constructor.f();
objA.constructor.f();
Object.getPrototypeOf(objB).constructor.f();
objB.constructor.f();
console.log(Object.getPrototypeOf(objB).constructor === objB.constructor);
console.log(Object.getPrototypeOf(objB) === B.prototype);.as-console-wrapper {
max-height: none !important;
}Note static properties exist in classes but not in instances.
Therefore, if you want to go from obj to its prototype, you should call Object.getPrototypeOf(obj), not obj.prototype, which is a completely different thing.
The .prototype property only exists in functions and, when instantiating a new object using new and a call to that constructor function (new A()), will become the newly created object's prototype (the deprecated .__proto__).
In your example:
obj.prototype; // undefined
A; // class A { static f() { ... } }
A.protoype; // { constructor: class A { ... } }
A.protoype.constructor; // class A { static f() { ... } }
A.protoype.constructor === A; // true
obj.constructor; // class A { static f() { ... } }
obj.constructor === A; // true
Object.getPrototypeOf(obj) === A.prototype; // true
obj.constructor is a Function hence shows an error, but works correctly when cast as <any>.
objis either an instance ofAorB?Object.getPrototypeOf(obj).constructor.f();works for meobj.constructor.f()is not a syntax error for sure. Did you mean you're getting a type error? If so, which one?obj.constructoris aFunctionhence shows an error, but works correctly when cast as<any>.Object.getPrototypeOf(obj).constructor.f()works.