factorialWithLambdaCalc.js

// Y Combinator
// makes the recursion
(function(improver) {
	return (function(gen) { return gen(gen) })(
	  function(gen) {
	    return improver(function(v) {
	      return gen(gen)(v)
	    })
	  }  
  )
})(
// this part is the condition for the factorial
  function(partial) {
    return function(n) {
      return n === 0 ? 1 : n * partial(n - 1)
    }
  }
// pass any number here to get its factorial
)(5)