Learning JavaScript Data Structures and Algorithms - Third Edition

Iterative Fibonacci

We implement the fibonacci function in an iterative way, as follows:

function fibonacciIterative(n) {  if (n < 1) return 0;  if (n <= 2) return 1;   let fibNMinus2 = 0;
  let fibNMinus1 = 1;
  let fibN = n;
  for (let i = 2; i <= n; i++) { // n >= 2
    fibN = fibNMinus1 + fibNMinus2; // f(n-1) + f(n-2)
    fibNMinus2 = fibNMinus1;
    fibNMinus1 = fibN;
  }
  return fibN;
}