Recursion and ES6 Generator exercises

Countdown (recursive)

function countDown(num) {
  console.log(num)
  if (num !== 0) {return countDown(--num)}
}

Factorial generator

function* factorialGenerator() {
  sequence = [1]
  while (true) {
    yield sequence[sequence.length - 1]
    sequence.push((sequence.length + 1) * sequence[sequence.length - 1])
  }
}

Fibonacci (recursive and generator)

// I didn't actually figure this out :(
// I had to look it up and modify it to meet the spec (don't start with zero)
// ... but it helped me better understand things so I could make the fibonacci generator later
var fibonacci_series = function (n)
{
  if (n===1)
  {
    return [0, 1]
  }
  else
  {
    var s = fibonacci_series(n - 1)
    s.push(s[s.length - 1] + s[s.length - 2])
    if (s[0] === 0) {s.shift()}
    return s
  }
}

// And I did this one on my own
function* fibonacci() {
  var sequence = [1,1]
  while (true) {
    sequence.push(sequence[sequence.length - 2] + sequence[sequence.length - 1])
    yield sequence
  }
}