function* fibonacci() {
  let [a, b] = [0, 1];
  while (true) {
    yield a;
    [a, b] = [b, a + b];
  }
}

const fib = fibonacci();

const result = [];
for (let i = 0; i < 4; i++) {
  result.push(fib.next().value);
}

const sum = result.reduce((total, num) => total + num, 0);
console.log(sum);