Primes generator

primes.js

exports.generator = function() {
	var found = [];

	function isPrime(p) {
		for (var i = 0; i < found.length; i++) {
			var q = found[i];
			if (p % q === 0) return false;
			if (q * q > p) return true;
		}
		return true;
	}
	return function(cb) {
		var p;
		if (found.length === 0) {
			p = 2;
		} else {
			p = found[found.length - 1] + 1;
			while (!isPrime(p)) p++;
		}
		found.push(p);
		cb(null, p);
	}
}

printPrimes._js

var nextPrime = require('./primes').generator();

for (var i = 0; i < 20; i++) console.log(nextPrime(_));