Implement fibonacci with Bottom-Up Style

fibonacciLoop.js

function fib(n) {
  let first = 1, second = 0;
  let current;
  for (let i = 2; i <= n; i++) {
    current = first + second
    second = first
    first = current
  }
  return current
}

console.assert(fibonacciLoop(3) === 2);
console.assert(fibonacciLoop(4) === 3);
console.assert(fibonacciLoop(5) === 5);
console.assert(fibonacciLoop(6) === 8);
console.assert(fibonacciLoop(7) === 13);