fib2.js

"use strict";

/**
 * Generate numbers in the Fibonacci sequence in a given interval.
 *
 * @generator
 * @function fibInInterval
 * @param {bigint|number} min - The lower limit of the interval.
 * @param {bigint|number} max - The upper limit of the interval.
 * @yields {bigint} The next number in the Fibonacci sequence respecting the interval.
 */
function *fibInInterval (min, max) {
  if (
    min < 1n ||
    max < 1n
  )
    throw new TypeError(`min (${min}) and max (${max}) must be superior or equal to 1.`);

  if (max < min)
    throw new TypeError(`max (${max}) must be superior to min (${min}).`);

  let n1 = 1n,
      n2 = 1n;

  for (; n2 < min; [n1, n2] = [n2, n1 + n2])
    ;

  for (; n2 <= max; [n1, n2] = [n2, n1 + n2])
    yield n2;
}