class Foo {
  constructor() {
    this.x = 1;
    this.self = this;
  }
  m() { return this.x; };
  getSelf() { return this }

  test() {
    const Foo = this;
    const o = { Foo: Foo };
    const fn = function () {
      return o;
    };

    expect((Foo?.["m"])()).toEqual(1);
    expect((Foo?.["m"])().toString).toEqual(1..toString);
    expect((Foo?.["m"])().toString()).toEqual('1');

    expect(((Foo?.["m"]))()).toEqual(1);
    expect(((Foo?.["m"]))().toString).toEqual(1..toString);
    expect(((Foo?.["m"]))().toString()).toEqual('1');

    expect((o?.Foo.m)()).toEqual(1);
    expect((o?.Foo.m)().toString).toEqual(1..toString);
    expect((o?.Foo.m)().toString()).toEqual('1');

    expect((((o.Foo?.self.getSelf)())?.m)()).toEqual(1);
    expect((((o.Foo.self?.getSelf)())?.m)()).toEqual(1);

    expect((((fn()?.Foo?.self.getSelf)())?.m)()).toEqual(1);
    expect((((fn?.().Foo.self?.getSelf)())?.m)()).toEqual(1);
  }

  testNull() {
    const o = null;

    expect(() => { (o?.Foo.m)() }).toThrow();
    expect(() => { (o?.Foo.m)().toString }).toThrow();
    expect(() => { (o?.Foo.m)().toString() }).toThrow();

    expect(() => { (((o.Foo?.self.getSelf)())?.m)() }).toThrow();
    expect(() => { (((o.Foo.self?.getSelf)())?.m)() }).toThrow();

    expect(() => (((fn()?.Foo?.self.getSelf)())?.m)()).toThrow();
    expect(() => (((fn?.().Foo.self?.getSelf)())?.m)()).toThrow();
  }
}

(new Foo).test();
(new Foo).testNull();