js to confirm fibonnaci

1function isFibonacci(n) {
2  var fib,
3    a = (5 * Math.pow(n, 2) + 4),
4    b = (5 * Math.pow(n, 2) - 4)
5
6  var result = Math.sqrt(a) % 1 == 0,
7    res = Math.sqrt(b) % 1 == 0;
8
9  //fixed this line
10  if (result || res == true) // checks the given input is fibonacci series
11  {
12    fib = Math.round(n * 1.618); // finds the next fibonacci series of given input
13    console.log("The next Fibonacci number is " + fib);
14
15  } else {
16    console.log(`The given number ${n} is not a fibonacci number`);
17  }
18}
19
20$('#fib').on("keyup change", function() {
21  isFibonacci(+this.value)
22})