rocket.chat.mqtt/node_modules/shortid/lib/is-valid.js

It's a MQTT Server, using redis to scale horizontally.

'use strict';
var alphabet = require('./alphabet');

function isShortId(id) {
    if (!id || typeof id !== 'string' || id.length < 6 ) {
        return false;
    }

    var characters = alphabet.characters();
    var len = id.length;
    for(var i = 0; i < len;i++) {
        if (characters.indexOf(id[i]) === -1) {
            return false;
        }
    }
    return true;
}

module.exports = isShortId;