javascript: prime number generator

prime_generator.js

var PrimeGenerator = function() {
	// 初始化的素数
	this.prime = 1;

	// 判断是否是素数
	this.isPrime = function(num) {
		var result = true;
		if (num !== 2) {
			if (num % 2 == 0) {
				result = false;
			} else {
				for (var x = 3, max = Math.sqrt(num); x <= max; x += 2) {
					if (num % x == 0) {
						result = false;
					}
				}
			}
		}
		return result;
	}

	// 查找下1个素数
	this.nextPrime = function() {
		this.prime++;
		while(!this.isPrime(this.prime)) this.prime++;
		return this.prime;
	}
}