return array of primes below limit using Sieve of Atkin Algorithm http://en.wikipedia.org/wiki/Sieve_of_Atkin #JavaScript #primes

JavaScript Sieve Of Atkin.js

function sieveOfAtkin(limit){
   var limitSqrt = Math.sqrt(limit);
   var sieve = [];
   var n;

   //prime start from 2, and 3
   sieve[2] = true;
   sieve[3] = true;

   for (var x = 1; x <= limitSqrt; x++) {
       var xx = x*x;
       for (var y = 1; y <= limitSqrt; y++) {
           var yy = y*y;
           if (xx + yy >= limit) {
             break;
           }
           // first quadratic using m = 12 and r in R1 = {r : 1, 5}
           n = (4 * xx) + (yy);
           if (n <= limit && (n % 12 == 1 || n % 12 == 5)) {
               sieve[n] = !sieve[n];
           }
           // second quadratic using m = 12 and r in R2 = {r : 7}
           n = (3 * xx) + (yy);
           if (n <= limit && (n % 12 == 7)) {
               sieve[n] = !sieve[n];
           }
           // third quadratic using m = 12 and r in R3 = {r : 11}
           n = (3 * xx) - (yy);
           if (x > y && n <= limit && (n % 12 == 11)) {
               sieve[n] = !sieve[n];
           }
       }
   }

   // false each primes multiples
   for (n = 5; n <= limitSqrt; n++) {
       if (sieve[n]) {
           x = n * n;
           for (i = x; i <= limit; i += x) {
               sieve[i] = false;
           }
       }
   }

   //primes values are the one which sieve[x] = true
   return sieve;
}

primes = sieveOfAtkin(5000);

Why line line 12 y is instanciate with 1 ? Should it not be y = x ?

This a performance friendly implementation as stated in wikipedia. But the output seems to be useless cause indexes of an array as the prime numbers cant be used anywhere.
See this link for a converter I coded to return a list of actual prime numbers.
https://gist.github.com/farskid/3501b1b981607483a46b76d61e092e6e