Check if object is a 'direct instance' of a class

Question

I have two classes:

class Bar extends Foo { // Foo isn\'t relevant
  constructor(value) {
    if (!(value instanceof Foo)) throw \"InvalidArgumentException:          


        

Answer 1

Check the constructor:

if (!value || value.constructor !== Foo)
  throw 'InvalidArgumentException: (...)';

or the prototype of the object (this is more similar to what instanceof does):

if (!value || Object.getPrototypeOf(value) !== Foo.prototype)
  throw 'InvalidArgumentException: (...)';