Aê...

prime.js

function isPrime(n) {
 if (n%1 || n<2) return false; 
 if (n%2==0) return (n==2);
 var m=Math.sqrt(n);
 for (var i=3;i<=m;i+=2) {
  if (n%i==0) return false;
 }
 return true;
}

var x = 0;
var a = [];

while(x<100){
	if(isPrime(x)) {
		a.push(x);
	}
	x++;
}

var fs = require('fs');
var outfile = "prime.txt";
var out = a.join(",");
fs.writeFileSync(outfile, out);
console.log(out);