https://stackoverflow.com/questions/7238586/do-i-need-to-be-concerned-with-race-conditions-with-asynchronous-javascript/7238663#7238663
https://stackoverflow.com/questions/7868434/are-calls-to-javascript-methods-thread-safe-or-synchronized/7868445#7868445
https://stackoverflow.com/questions/7575589/how-does-javascript-handle-ajax-responses-in-the-background/7575649#7575649
