Differnt styles of factorial implemetation in js for fun

fac.js

/** Newbie Programmer */
function fac(n) {
 if(n === 0)
  return 1;
 else
  return n * fac(n-1);
}

/** Callback programmer */
function fact(n, cback) {
    function nextFact(n, acc) {
        if (typeof n !== 'number') {
            cback(new Error('Not a number'), null);
        } else if (n < 0) {
            cback(new Error('Less than zero'), null);
        } else if (n === 0) {
            cback(null, acc);
        } else {
            nextFact(n - 1, acc * n);
        }

    }
    setTimeout(nextFact(n, 1), 0);
}

/** Promise Programmer */
var fac = function(n) { 
  return new Promise(function (res,rej) { 
    if(n == 1) 
      res(1);
    else 
      fac(n-1).then(function(result) {
        res(result * n);
      }); 
  }); 
}

fac(n).then(function(res) {
   console.log(res); 
});

/** Generator programmer */
var fac_gen = function* (n, acc) {
  if (n === 0) {
    return acc;
  } else {
    yield fac_gen(n - 1, n * acc);
  }
};

var fac = function (n) {
  var c = fac_gen(n, 1);
  var d = {};
  while (!d.done) {
    d = c.next();
    c = d.value;
  }  
  return d.value;
}

/** Lazy Programmer */
function Mult(n) {
  return function () {
    return [n+1, Mult(n+1)];
  }
}

function apply(f) {
  return typeof f === "function" ? f() : f;
}

function take(n, g) {
   if(n) {
     var xs = apply(g);
     return xs[0] * take(n-1, xs[1])
   } else {
     return 1;
   }
}

take(n, Mult(0)) // => Same as fac(n)

/* combinatory Programmer */
fuhction Y(x) {
 return function (n) {
  return x(x)(n);
 }
}

var fac = Y(function (fac) {
 return function (n) {
  return n === 0 ? 1 : n * fac(fac)(n-1)
 }
})

/=> fac(n)