JSFiddle - React, Tailwind, and code Playground

by Gabriel Vazquez

JavaScript

// < 4,000,000
// Fibonacci 1, 2, 3, 5, 8, 13, 21, 34, 55, 89

const isEven = (num) => {
  return (num % 2 === 0);
};

const fibonacci = (max) => {
  let sum = 2;
  let f;
  let nums = [1, 2];
  let n = 1;
  do {
    f = nums[n-1] + nums[n];
    n++;
    nums.push(f);
    if(isEven(f)) {
      sum += f;
    }
  } while((f < max));
  return sum;
}

alert(fibonacci(4000000));