JavaScript client side application state, using session storage.

app-state.js

/*global define:true, sessionStorage:true*/
define([
    "underscore"
], function(_) {
    "use-strict";

    var appState, sessionStorageNamespace;

    sessionStorageNamespace = "app.appState";

    function AppState(supportSessionStorage) {
        this.supportSessionStorage = supportSessionStorage;
        this.myId = null;
    }

    AppState.prototype.getMyId = function() {
        return this.myId;
    };

    AppState.prototype.setMyId = function(myId) {
        this.myId = myId;
        this.persist();
    };

    AppState.prototype.persist = function() {
        // if we support session storage, persist ourselves
        if (this.supportSessionStorage) {
            sessionStorage.setItem(sessionStorageNamespace, JSON.stringify(this));
        }
    };

    if (typeof sessionStorage != "undefined") {
        // attempt to load from the session storage
        appState = sessionStorage.getItem(sessionStorageNamespace);
        if (appState) {
            appState = _.extend(new AppState(true), JSON.parse(appState));
        } else {
            // it wasn't found, but we do support session storage
            appState = new AppState(true);
        }
    } else {
        // we don't support session storage
        appState = new AppState(false);
    }

    return appState;
});