Y Combinator in Javascript

Y_Combinator.js

var y = function(le) {
  return function(f) {
    return f(f);
  }(function(f) {
    return le(
      function(x) {
        return (f(f))(x);
      }
    );
  });
};


var factorial = y(function(fac) {
  return function(n) {
    return n <= 2 ? n : n * fac(n - 1);
  };
});

/*
var yo = function(f) {
  return le(function(x) {
    return (f(f))(x);
  });
};

var y = function(le) {
  return function(f) {
    return f(f);
  }(yo);
};

var factorial = y(function(fac) {
  return function(n) {
    if (n <= 2) {
      return n;
    } else {
      return n * fac(n - 1);
    }
  };
});
*/

var number120 = factorial(5);
number120 === 120;