factorial.js

let factorial = number =>
  (z =>
    (s =>
      (_a =>
        (a =>
          (_m =>
            (m =>
              (_f =>
                (f =>
                  (_tF =>
                    (tF =>
                      (_tI =>
                        (tI =>
                          tI(f(tF(number)))
                        )(n => _tI(_tI)(n))
                      )(tI => n => n(() => 0)(p => 1 + tI(tI)(p)))
                    )(n => _tF(_tF)(n))
                  )(tF => n => n < 1 ? z : s(tF(tF)(n - 1)))
                )(n => _f(_f)(n))
              )(f => n => n(() => s(z))(p => m(n)(f(f)(p))))
            )(p => q => _m(_m)(p)(q))
          )(m => p => q => p(() => z)(pp => q(() => z)(qp => a(m(m)(pp)(q))(q))))
        )(m => n => _a(_a)(m)(n))
      )(a => m => n => m(() => n)(mp => a(a)(mp)(s(n))))
    )(p => x => y => y(p))
  )(x => y => x());