Factorial! factory.

factorializer.js

function factorialize(num) {

  var facArray = [];

  if (num === 0) {
    return 1;        
    } else {
    for (var i = 1; i <= num; i++) {
      facArray.push(i);
    }
    return facArray.reduce(function(a, b) { return a * b; });
  }
}

factorialize(5);