Validate a Number as Fibonacci Series Number in JavaScript

We are required to write a JavaScript function that takes in a number and checks whether it falls in Fibonacci series or not.

We should return a boolean on this basis.

Example

The code for this will be −

const num = 89;
const isFib = query => {
   if(query === 0 || query === 1){
      return true;
   }
   let prev = 1;
   let count = 2;
   let temp = 0;
   while(count >= query){
      if(prev + count === query){
         return true;
      };
      temp = prev;
      prev = count;
      count += temp;
   };
   return false;
};
console.log(isFib(num));

Output

Following is the output on console −

true