Fibonacci

fib_iterative.js

function fib_i(num) {
  console.log(`Series of ${num}`);
  let num2 = 0, num1 = 1;
  for (let i = 0; i < num; i++) {
    console.log(num1);
    const next = num2 + num1;
    num2 = num1;
    num1 = next;
  }
}

fib_recursive.js

function fib_r(num) {
  if (num <= 1) {
    return 1;
  }
  let num2 = fib_r(num - 2),
      num1 = fib_r(num - 1);
  let next = num1 + num2;
  return next;
}