Find fibonacci numbers using perfect square formula

fibonacci.js

/**
 * The question may arise whether a positive integer x is a Fibonacci number. This is true if and only if one or both of 5x^{2}+4 or 5x^{2}-4 is a perfect square.
 * https://en.wikipedia.org/wiki/Fibonacci_number#Recognizing_Fibonacci_numbers
 */

// the first 20 fibonacci numbers are found 0->6765
Array.from(generate(6765+1))
   .map((i, idx) => ({number: i, isFibonacci: isFibonacciNumber(i)}))
   .filter(kv => kv.isFibonacci)
   .map((kv, index) => console.log(`found ${1+index}th fibonacci number: ${kv.number}`));


function isFibonacciNumber(n) {
  return n == 0 ||
    (n >= 0 && (isPerfectSquare(5 * n * n + 4) || isPerfectSquare(5 * n * n - 4)));
}

// perfect square - square root of given value is an integer number
function isPerfectSquare(value) {
  const sqrt = Math.sqrt(value);
  return (sqrt | 0) === sqrt;
}

function* generate(length) {
  var idx = 0;
  while(idx < length) {
    yield idx++;
  }
}