Check Whether a Number is a Fibonacci Number or Not in JavaScript

We are required to write a JavaScript function that takes in a number and returns a boolean based on the fact whether or not it comes in the fibonacci series.

For example −

If the function call is like this −

fibonacci(12);
fibonacci(89);
fibonacci(55);
fibonacci(534);

Then the output should be −

False
true
true
false

Now, let’s write a recursive solution to this problem −

Example

const fibonacci = (query, count = 1, last = 0) => {
   if(count < query){
      return fibonacci(query, count+last, count);
   };
   if(count === query){
      return true;
   }
   return false;
};
console.log(fibonacci(12));
console.log(fibonacci(55));
console.log(fibonacci(89));
console.log(fibonacci(534));

Output

The output in the console will be −

false
true
true
false