Countdown with recursion

countdown.js

function countdown(number) {
  if (number !== 0) {
   console.log(number);
   countdown(number - 1);
  } else {
    console.log(0);
  }
}

countdown(5);

factorial_generator.js

function* factorialGenerator() {
  var total = 0;
  var num   = 1;

  while(true) {
    total += num;
    num   += 1;
  yield total;

  }

}

var factorial = factorialGenerator();

console.log(factorial.next().value); // 1
console.log(factorial.next().value); // 2
console.log(factorial.next().value); // 6
console.log(factorial.next().value); // 10
console.log(factorial.next().value); // 15

fib.js

function fibonacci(length, sequence) {

  var fibSequence       = sequence || [1, 1];
  var fibSequenceLength = fibSequence.length;

  if        (length === 0) { console.log( fibSequence );
  } else if (length === 1) { console.log( [1]         );
  } else if (length === 2) { console.log( fibSequence );
  } else {
    var nextFibNum =
       fibSequence[fibSequence.length - 2] +                            fibSequence[fibSequence.length - 1];

    fibSequence.push(nextFibNum);

    fibonacci(length - 1, fibSequence);
  }

}

fibonacci(1);
fibonacci(2);
fibonacci(3);
fibonacci(4);
fibonacci(10);