You can use ivars so you don't need to make so many hilarious classes

classWithIvar.cocoascript.js

class Class {
  constructor(ivars = []) {
    const uniqueClassName = "fetchDelegate_" + NSUUID.UUID().UUIDString();
    const cls = MOClassDescription.allocateDescriptionForClassWithName_superclass_(uniqueClassName, NSObject);
    
    const prototype = Object.getPrototypeOf(this);
    Object.getOwnPropertyNames(prototype).forEach(prop => {
      console.log(prop);
      const sel = NSSelectorFromString(prop);
      cls.addInstanceMethodWithSelector_function_(sel, prototype[prop]);
    })

    ivars.forEach(ivar => {
      cls.addInstanceVariableWithName_typeEncoding(ivar, "@");
    })
    const instance = cls.registerClass().new();
    this._instance = instance;
    return this;
  }

  get(key) {
    return this._instance.valueForKey(key)
  }

  set(key, value) {
    return this._instance.setValue_forKey(value, key)
  }
}

class MySillyClass extends Class {
  fooFooFoo() {
    const foo = this.get('foo');
    return foo + foo + foo;
  }
}

const inst = new MySillyClass(['foo', 'bar', 'baz'])
inst.set('foo', 'bar');
log(inst.get('foo'))
log(inst.fooFooFoo())