Find all classes in a Javascript application that extend a base class

I have code like this

class Animal{}
class Dog extends Animal {}
class Cat extends Animal {}
class Donkey extends Animal {}

I want to look at all of the classes in my application’s universe, and when I find one that descends from Animal, I want to create a new object of that type and add it to the list. This allows me to add functionality without having to update a list of things. So I can avoid the following:

var animals = [];
animals.push( new Dog() );
animals.push( new Cat() );
animals.push( new Donkey() );

PS: I don’t want to add extra functionality to my classes or call them explicitly.

Answer

Here what I discovered so far http://jsbin.com/xiroyurinu/1/edit?js,console,output

class Animal{}
class Dog extends Animal {}
class Cat extends Animal {}
class Donkey extends Animal {}

var animals = getAllSubclasses(Animal);

console.log(animals.map(function(c){ return new window[c] })) // creates objects
document.body.innerText = animals; // Dog, Cat, Donkey

and the magic

function getAllSubclasses(baseClass) {
  var globalObject = Function('return this')(); 
  var allVars = Object.keys(globalObject);
  var classes = allVars.filter(function (key) {
  try {
    var obj = globalObject[key];
        return obj.prototype instanceof baseClass;
    } catch (e) {
        return false;
    }
  });
  return classes;
}

The main disadvantage of this method is that I can not use ES6 module import and have to do old fashioned and simple contatenation of files, but this is still better that nothing.

PS: still wait for better answer

UPD: and ye, i know that to use this all classes must be defined globally, that’s why i search for better way to do this..