How to implement abstract factory method in JavaScript?

So how to use abstract factory method in JavaScript? For example in Java:

public abstract class SuperClass {
    abstract String bar();

    public String foo() {
        return bar();
    }
}

public class SubClass extends SuperClass{
    @Override
    String bar() {
        return "bar";
    }
}

public class Test {
    public static void main(String[] args) {
        System.out.println(new SubClass().foo());
    }
}

It shows bar and just fine. But when I tried this in JavaScript:

var SuperClass = function () {};
SuperClass.prototype.foo = function () {
    return this.prototype.bar();
};

var SubClass = function () {};
SubClass.prototype = Object.create(SuperClass.prototype);
SubClass.prototype.constructor = SubClass;

SubClass.prototype.bar = function () {
    return "bar";
};

var myClass = new SubClass();
console.log(myClass.foo());

I get Uncaught TypeError: Cannot read property 'bar' of undefined. I tracked the bug and turns out, when SuperClass.prototype.foo is being executed, SubClass.prototype is still undefined.

So, what's the right way to do that? Thanks you!