szurubooru/public_html/js/State.js

var App = App || {};

App.State = function() {

    var properties = {};
    var observers = {};

    function get(key) {
        return properties[key];
    }

    function set(key, value) {
        properties[key] = value;
        if (key in observers) {
            for (var observerName in observers[key]) {
                if (observers[key].hasOwnProperty(observerName)) {
                    observers[key][observerName](key, value);
                }
            }
        }
    }

    function startObserving(key, observerName, callback) {
        if (!(key in observers)) {
            observers[key] = {};
        }
        if (!(observerName in observers[key])) {
            observers[key][observerName] = {};
        }
        observers[key][observerName] = callback;
    }

    function stopObserving(key, observerName) {
        if (!(key in observers)) {
            return;
        }
        if (!(observerName in observers[key])) {
            return;
        }
        delete observers[key][observerName];
    }

    return {
        get: get,
        set: set,
        startObserving: startObserving,
        stopObserving: stopObserving,
    };

};

App.DI.registerSingleton('appState', [], App.State);