Well over a year ago I posted an article describing how to employ an asynchrony concept known as a Promise.  Since then a number of implementations of Promises have shown up in libraries such as jQuery Deferred and CommonJS.  I’ve updated the sources and removed the dependency on ASP.NET Ajax, however the current version depends on features of ECMAScript 5, which is supported in IE 9, Chrome, and Firefox.  If you need support for Safari, Opera, or IE 8 and under you need to use an ES5 Polyfill.  In addition the license has been changed from MSR-LA (Non-Commercial) to MS-PL which allows commercial use.