secret

#1.js

(function (n) {
    return Array.prototype.join.call({length: n + 1}, 0).split("").reduce(function (prev, curr, i, arr, undef) {
        return (!(i%3) || !(i%5)) && i > 0 ? prev.push(i) && prev : prev;
    }, []).reduce(function (a, b) {return a + b;});
}(1000)) //233168

#2.js

(function (limit) {
    return (function r(arr, limit) {
        var n = arr[arr.length - 1] + arr[arr.length - 2];
        return n < limit ? (arr.push(n), r(arr, limit)) : arr;
    }([0, 1], limit)).reduce(function (a, b) {
        return !(b%2) ? a + b : a;
    });
}(4000000)) //4613732

#3.js

function isPrime(n) {
    var a = Math.floor(Math.sqrt(n));
    while (a > 1) {
        if (!(n%a)) {
            return false;
        }
        a -= 1;
    }    
    return true;
}
function nextPrimeFactor(n, composite) {
    var i = composite ? n || 1 : 1;
    while (i += 2) {
        if (!(composite%i) && isPrime(i)) {
            return i;
        }
    }
}
(function (composite) {
    var primeFactors = [1];
    while (primeFactors.reduce(function (a,b) {return a*b;}, 1) < composite) {
        primeFactors.push(nextPrimeFactor(primeFactors[primeFactors.length - 1], composite));
    }
    return primeFactors[primeFactors.length - 1];
}(600851475143));

#4.js

function factor(n) {
    var i = 999;
	while (n%i) {
		i -= 1;
	}
	return i;
}
function nextPalindrome(n) {
    var s = n + "";
    var p1 = s.substr(0,s.length/2);
    p1 = Number(p1) - 1;
    var p2 = (p1 + "").split("").reverse().join("");
    return Number(p1 + p2);
}
(function (n) {
    var p = nextPalindrome(n);
    var f = factor(p);
    while (f < 100 || p/f > 999) {
        p = nextPalindrome(p);
        f = factor(p);
    }
    return [p, f, p/f];
}(999*999))

#5.js

var arr = (function (result, n, len) {
    var i = n;
    for (; i <= len; i += 1) {
        result.push(i);
    }
    return result;
}([], 1, 20));
function isPrime(n) {
    var a = Math.floor(Math.sqrt(n));
    while (a > 1) {
        if (!(n%a)) {
            return false;
        }
        a -= 1;
    }    
    return true;
}
var primes = (function (results, n) {
    while (n > 1) {
        if (isPrime(n)) {
            results.push(n);
        }
        n -= 1;
    }    
    return results;
}([], 20));
var leap = primes.reduce(function (a, b) {return a*b;});
function factorable(n) {
    return arr.every(function (i) {
        return !(n%i);
    });
}
(function (L) {
    var n = L;
    while (!factorable(n)) {
        n += L;
    }
    return n;
}(leap)); //232792560

#6.js

(function (a, b) {
    var i, result = 0;
    for (i = a; i < b + 1; i += 1) {
        result += i;
    }
    return result * result;
}(1, 100)) - (function (a, b) {
    var i, result = 0;
    for (i = a; i < b + 1; i += 1) {
        result += i * i;
    }
    return result;
}(1, 100)) //25164150

#7.js

function isPrime(n) {
    var a = Math.floor(Math.sqrt(n));
    while (a > 1) {
        if (!(n%a)) {
            return false;
        }
        a -= 1;
    }    
    return true;
}
(function (n) {
    var primes = [2, 3];
    var p = 3;
    while (primes.length < n) {
        p += 2;
        while (!isPrime(p)) {
            p += 2;
        }
        primes.push(p);
    }
    return primes[primes.length - 1];
}(10001)); //104743

#8.js

var n = "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450";
Math.max.apply(null, n.split("0").map(function (a) {
    var str = a, val = 0;
    while (str.length > 4) {
        val = Math.max(str.substr(0,5).split("").reduce(function (d, e) {
            return d * e;
        }, 1), val);
        str = str.substr(1);
    }
    return val;
}));
//40824

#9.js

(function (n) {
    var i, j, k, evenk;
    for (i = 1; i < n; i += 1) {
        for (j = i + 1; j < n; j += 1) {
            evenk = i%2 && j%2;
            for (k = evenk ? j + 1 : j + 2; k < n; k += 2) {
                if ((i * i) + (j * j) === (k * k) && i + j + k === 1000) {
                    return [i, j, k];
                }
            }
        }
    }
}(1000)); //[200, 375, 425]

#5 in Erlang:

gcd(X, 0) -> X;
gcd(X, Y) -> gcd(Y, X rem Y).
lcm(X, Y) -> abs(X*Y div gcd(X,Y)).
run() -> lists:foldl(fun lcm/2, 20, lists:seq(1, 19)).