function FibonacciSeriesRecursive(index) { if(index<2) { return index; } return FibonacciSeriesRecursive(index-2) + FibonacciSeriesRecursive(index-1) } console.log(FibonacciSeriesRecursive(10)); function fibonacciSeriesIterative(num) { const arr1 = [0,1]; for(let i=2; i <= num; i++) { arr1.push(arr1[i-2]+arr1[i-1]); } return arr1[num]; } console.log(fibonacciSeriesIterative(10));