SharePoint: Using deferreds/Promises Or Callbacks in Javascript client object model

http://www.sharepointnadeem.com/2014/10/sharepoint-using-deferredspromises-or.html

https://social.msdn.microsoft.com/Forums/sqlserver/en-US/09d122a4-943f-4db6-ae6f-7454e11ec3b5/jsom-executequeryasync

http://sharepoint.stackexchange.com/questions/97656/js-library-for-rest-and-jsom-sharepoint-basic-tasks

http://sharepoint.stackexchange.com/questions/144512/jsom-promise-method-on-sharepoint-2010-site

http://blog.qumsieh.ca/2013/10/31/using-jquery-promises-deferreds-with-sharepoint-2013-jsom/