Problem

Write a generator function that returns a generator object which yields the fibonacci sequence.

The fibonacci sequence is defined by the relation Xn = Xn-1 + Xn-2.

The first few numbers of the series are 0, 1, 1, 2, 3, 5, 8, 13.

Example 1:

Input: callCount = 5 Output: [0,1,1,2,3] Explanation: const gen = fibGenerator(); gen.next().value; // 0 gen.next().value; // 1 gen.next().value; // 1 gen.next().value; // 2 gen.next().value; // 3

Example 2:

Input: callCount = 0 Output: [] Explanation: gen.next() is never called so nothing is outputted

Constraints:

0 <= callCount <= 50

Pre analysis

Implementing with generator function without caching/memoization.

Another solution

/**
 * @return {number[]}
 */
function* fibGenerator() {
  let [a, b] = [0, 1];
  while (true) {
    yield a;
    [a, b] = [b, a + b];
  }