eratosthenes.js

eratosthenes = function(max){
    
    var nums = [];
    var primes = [];
    
    for(var i = 2; i <= max; i++){
        nums.push(i);
    }
    
    var sqrt = Math.sqrt(max);
    while(nums[0]<=sqrt){
        var prime = nums.shift();
        primes.push(prime);
        nums = nums.filter(function(num){
            return num % prime != 0
        });
    }
    
    return primes.concat(nums);
}

// == main == 
console.log(eratosthenes(50));

// [ 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47 ]