Randomly Generates primes from first 100 using Javascript

genPrime.html

<!-- Author: Mahbub -->

<h1 id="prime">2</h1>
<p>is a prime number</p>
<!-- Randomly Generates primes from first 100 -->
      <script>
         var primes=[-1, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163 ,167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541]; 
         var index = Math.floor((Math.random() * (primes.length - 1)) + 1);
         if (index >= 1 && index <= (primes.length - 1))
            document.getElementById("prime").innerHTML = primes[index];
         else
            document.getElementById("prime").innerHTML = primes[2];
      </script>