JSFiddle - React, Tailwind, and code Playground

JavaScript

var memo = [];

function getFib(n) {
  if (memo[n])
    return memo[n];
  if (n == 1 || n == 2)
    return 1;
  memo[n] = getFib(n - 1) + getFib(n - 2);
  return memo[n];
}

console.log(getFib(5));