How many unique jsbin url shortcode combinations can exist?

Question

This is jsbin's function that generates each bin's identification shortcode:

function shortcode() {
    var vowels = 'aeiou',
        consonants = 'bcdfghjklmnpqrstvwxyz',
        word = '', length = 6, index = 0, set;

    for (; index < length; index += 1) {
        set = (index % 2 === 0) ? vowels : consonants;
        word += set[Math.floor(Math.random() * set.length)];
    }

    return word;
}

How many different combinations could it produce? If I've calculated well, there are 3.08915776e+8 combinations when using 6 letters from a set of 26 letters(a-z). But how would this be calculated, since there are sets of 5(vowels) and sets of 21(consonants) alternating to produce memorizable shortcodes like 'ecamit', 'izafij', 'erowih', 'avimog' etc...

Would that be (5x21)^3 = 121,550,625 ?

score 1 · Answer 1 · answered Sep 01 '13 at 11:11

The shortcode method was recently updated because we kept hitting duplicates too often, and in fact the version of code you see also appended numbers on the end to increase force them to become unique.

I believe the number of variations, based on this code alone (the code above, not what's in jsbin's production code base) is: 1,157,625 (5 * 21 * 5 * 21 * 5 * 21) - which really isn't much.

The simple method comes from my old password generator: http://remysharp.com/2008/04/14/pronounceablely-random/ - but recently I had to change it in jsbin's production.

It now keeps adding characters on each positive hit on the database, but also the letters are duplicated in uppercase, so the range of url combinations are much much higher now.

How many unique jsbin url shortcode combinations can exist?

1 Answers1