Untitled

<!DOCTYPE html>
<html>
<head>
<script>
function isPrime($n)
{
    $i=2;
if ($n==2){
return true;
}

$sqrtN = sqrt($n);
while ($i<= $sqrtN){
if ($n % $i ==0){
return false;
}
$i++;
}
return true;
}
</script>

</head>
<body>
Value: <input type="number" id="n"><br>
<input type="submit" value="Send" onclick="isPrime(n)">
</form>

<p id="derp">sdvfsdg</p>

<script>
document.getElementById("derp").innerHTML = isPrime(n);
</script>


</body>
</html>