var addTwoNumbers = function(l1, l2) {

  var e =

    l1

      .reverse()

      .map((v, index, array) => v * Math.pow(10, array.length - index - 1))

      .reduce(function(prev, next) {

        return prev + next

      }) +

    l2

      .reverse()

      .map((v, index, array) => v * Math.pow(10, array.length - index - 1))

      .reduce(function(prev, next) {

        return prev + next

      }) +

    ''

  return e.split('').map(Number)

}