Simulate the `instanceof` keyword.

myInstanceOf.js

function myInstanceOf(instance, constructor) {
  if (typeof constructor !== 'function') {
    throw Error(`The parameter 'constructor' is not a function!`)
  }

  let proto = instance.__proto__;
  const prototype = constructor.prototype;
  while (proto !== null) {
    if (prototype === proto) {
      return true;
    }
    proto = proto.__proto__;
  }

  return false;
}