Prime numbers code written in Node.js

primes.js

var fs = require("fs");
 function getPrimes(max) {
    
    var sieve = [], i, j, primes = [];
    for (i = 2; i <= max; ++i) {
        if (!sieve[i]) {
            // i has not been marked -- it is prime
            primes.push(parseInt(i));
            for (j = i << 1; j <= max; j += i) {
                sieve[j] = true;
            }
        }
    }
    return primes;
}
 function sortNumber(a,b)
    {
  return a - b;
                      }
  var numbs = getPrimes(54199);  
  numbs.sort(sortNumber);
  var outFile = "prime.txt"  
  
   for(var i=0;i<numbs.length-1;i++){
   fs.appendFileSync(outFile, numbs[i]+"," );}
   fs.appendFileSync(outFile, numbs[numbs.length-1] );