Fibonacci number. optimised algorithm

let getF = (n) => {
  
  if (n < 2) return n;

  var a = 0,
      b = 1,
      result;
      
  for (var i = 2; i <=n; i++ ){
      result = a + b;
      a = b;
      b = result;
  }

  return result;
}


let time = 0;
let result = 0;
for(let i = 500; i < 505; i++){
  time = performance.now();
  result = getF(i);
  console.log(`F at ${i} is ${result} took time: ${performance.now() - time} ms.`);
}