*Fibonacci numbers: All Star Code Challenge #10

//https://www.codewars.com/kata/58646a1173bd9c86080000ef/train/javascript



function  fibonacci(n){
if (n === 0) return 0;
let arr = [1,1], sum = 0;
  for (let i = 1; i <= n-2; i++){
    sum = arr[i-1] + arr[i];          //pay attention: don't store 'sum'!
    arr.push(sum);
  }
  return arr[n-1];                  //return last index.
}