Just a simple utility class for some callback handling.

ReadyListener.js

function ReadyListener(config) {
    this.properties = config || {};
    this.onReady = function() {};
}

ReadyListener.prototype.ready = function(key) {
    this.properties[key] === false && (this.properties[key] = true);
    var isReady = true;
    for(k in this.properties) isReady = isReady && this.properties[k];
    isReady && this.onReady();
}

ReadyListener.prototype.then = function(callback) {
    this.onReady = callback;
    return this;
}