gistfile1.js

function isFib(val) {
    var check1 = 5 * Math.pow(val, 2) + 4;
    var check2 = 5 * Math.pow(val, 2) - 4;
    
    function isPerfectSquare(num) {
        return Math.sqrt(num) % 1 === 0;
    }
    
    //we see if the checks are perfect squares
    var isPerfect1 = isPerfectSquare(check1); 
    var isPerfect2 = isPerfectSquare(check2);
    
    if(isPerfect1 && isPerfect2) {
        return true;
    }
    else if(isPerfect1 || isPerfect2) {
        return true;
    }
    else {
        return false;
    }

};


//do some tests

//return true
console.log(isFib(5));

//return false
console.log(isFib(9));

//return true
console.log(isFib(317811));

//return true
console.log(isFib(0));