After developing web applications for such a long time, there will be some functions and pieces of code that is always use.
Of course there are frameworks available for production. There is jQuery, Mootools (Just to name a few more popular ones), all great for extensive development.
Fast.js is open source, if anyone is interested in understanding how such a framework is developed, or perhaps want a base framework to improve your web development workflow, here is the bitBucket repository.
To see the Api documentation, visit this page, and to include it into your projects, include this line of code,
<script src="http://ongspxm.bitbucket.org/dev/fast.min.js"></scrip>, in the head section of your site, before all the other scripts are loaded.