Euler #3 javascript error -

i know may downvoted i've been frustrated 24 hours , looking @ other euler 3 threads hasn't helped me solve this. can code? think i'm close.

function is_prime(num) {     if (isnan(num)) return false;     (i=2; i<=math.sqrt(num); i++) {         if (num % === 0) {             return false;         }         else {             return true;         }     } } 

// above part correctly finds whether number prime or not. problem lies below part.

var holder = 0; function getbiggestprime (end) {     (i=2; i<=math.sqrt(end); i++) {         while (is_prime(i) && (end%i===0))              holder = i;             return holder;     } }  getbiggestprime(13195); console.log(holder); 

the first method not correct. corrected version be:

    <script> function is_prime(num) {     if (isnan(num)) return false;     (var i=2; i<=math.sqrt(num); i++) {         if (num % === 0) {             return false;         }             }     return true; } 

//same problem second method - return should after for-loop ends (also, change while if):

function getbiggestprime (end) {     var holder = end;     (var i=2; i<=math.sqrt(end)+1; i++) {         if (is_prime(i) && (end%i===0))              holder = i;                 }     return holder; } 

a link the demo.

about second part (if understand correctly you're looking for) should start from:
i = math.sqrt(end) , go down i-- until find biggest prime.