( function() {
    var chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';

    base62 = {
        encode: function(n) {
            var s = '';

            do {
                s = chars[n % 62] + s;
            }
            while ( n = Math.floor(n / 62) );

            return s;
        },

        decode: function(s) {
            var q = s.length,
                w,
                e = 0,
                r = 0;

            while (q--) {
                if ( w = chars.indexOf(s[q]) ) {
                    r += w * Math.pow(62, e);
                }

                ++e;
            }

            return r;
        }
    }
} )();