util.js

var DICTIONARY = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".split('');

function generateID(seed) {
    /* Given a seed, this function will return a 'shortened' URL */
    if (typeof(seed) === 'undefined') seed = new Date().getTime();
    return encode(seed);
}

function getSeedFromID(id) {
    /* Given a 'shortened' URL, it will return the seed */
    if (typeof(seed) === 'undefined') return -1;
    return decode(id);
}

function encode(i) {
    /* Generates a 'shortened' URL */
    if (i == 0) return DICTIONARY[0];

    var result = '';
    var base = DICTIONARY.length;

    while (i > 0) {
        result += DICTIONARY[i % base];
        i = Math.floor(i / base);
    }

    return result;
}

function decode(i) {
    /* Returns the original input from a 'shortened' URL */
    var i = 0;
    var base = DICTIONARY.length;

    input.split("").forEach(function (c) {
        i = i * base + DICTIONARY.indexOf(c);
    });

    return i;
}

exports.makeid = function makeid() {
    var text = "";
    var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

    for (var i = 0; i < 5; i++)
        text += possible.charAt(Math.floor(Math.random() * possible.length));

    return text;
}

exports.getRandomK = function (array, k) {
    var shuffled = exports.shuffle(array);
    return shuffled.slice(0, k);
};

exports.shuffle = function (array) {
    var tmp, current, top = array.length;

    if (top) while (--top) {
        current = Math.floor(Math.random() * (top + 1));
        tmp = array[current];
        array[current] = array[top];
        array[top] = tmp;
    }

    return array;
}