Fibonacci number generation with recursive function.

fibonacci-recursive.js

function fibonacci(index) {
  if (index == 0) {
    return 0;
  } else if (index == 1) {
    return 1;
  } else {
    return fibonacci(index - 2) + 
        fibonacci(index - 1)
  }
}

fibonacci(0);
fibonacci(1);
fibonacci(2);
fibonacci(3);