Sieve

sieve.js

var computePrimes = function(limit) {
    var sieve = [];
    for (var i = 2; i < limit; i++) {
        if (sieve[i] === false) {
            continue;
        }
        for (var j = 2; j * i < limit; j++) {
            sieve[j * i] = false;
        }
    }
    
    var primes = [];
    for (var i = 2; i < limit; i++) {
        if (sieve[i] !== false) {
            primes.push(i);   
        }
    }
    return primes;
};
            
console.log(computePrimes(100));

http://en.wikipedia.org/wiki/Sieve_of_Eratosthenes