function evenFiboSum(ceilingValue) {

	let sum = 0;
	let x = 1;
	let y = 2;

	while (x <= ceilingValue) {

		if (x % 2 == 0) {
			sum += x;
		}

		y = x + y;
		x = y - x;

	}

	return sum;
}

console.log(evenFiboSum(4000000));