JAVASCRIPT

js get fibonacci number

/**
 * Method that calculates the Fibonacci Sequence and returns the n'th value of the sequence
 * @param {*} pos 
 */
const getFibPosition = (pos) => {
    if (pos === 0) return null;
    if (pos === 1) return 0;
    if (pos === 2) return 1;

    let fibArray = [0, 1];
    let aux1, aux2;

    for (let i = 2; i < pos; i++) {
        aux1 = fibArray[i - 1];
        aux2 = fibArray[i - 2];

        fibArray.push(aux1 + aux2);
    }

    return fibArray[pos - 1];
}

js how to get n fibonacci number

function getFibonacci(n) {
    let a = 1;
    let b = 1;

    for (let i = 3; i <= n; i++) {
      let c = a + b;
      a = b;
      b = c;
    }

    return b;
  }

  console.log(getFibonacci(3)); // => 2
  console.log(getFibonacci(7)); // => 13
  console.log(getFibonacci(20)); // => 6765
  console.log(getFibonacci(77)); // => 5527939700884757