fibonacci-number.js

/**
 * @param {number} n
 * @return {number}
 */
// The Iterative Approach
var fibIterativeApproach = function (n) {
    if (n <= 1) return n;
    let prev1 = 0, prev2 = 1, current;

    for (let i = 2; i <= n; i++) {
        current = prev1 + prev2;
        prev1 = prev2;
        prev2 = current;
    }

    return current;
};
// fibIterativeApproach(5)