factorialize.js

function factorialize(num) {
    factorialArr = [];
    
    if (num === 0) {
        factorialArr = [1];
    } else {
        for (i = 1; i < num + 1; i++) {
        factorialArr.push(i);
        }
    }
  
  var factorial = 0;
  
  factorialArr.reduce(function(previousValue, currentValue) {  
      return factorial = previousValue * currentValue;
  }, 1);
  return factorial;
}