Single Page Application, a fundamental requirement for SPA is to develop the application with XMLHttpRequest (XHR) or AJAX. That is only main requirement, other things come as add-on stuff. Advancements of SPA? In today's world, we do not want to be restricted with basic features or functionalities. We want everything like any new Phone comes in market with some new shiny feature. There are a lot of functionalities available with SPA libraries and could be extended with more extension to have richer and easier implementation. To be specific we shall refer it as frameworks, not libraries. Earlier days one-way, two-way data binding with templates were very minimum things to expect from frameworks. Now they talk about component structure, Virtual Dom, IOC, state management, performance etc. Why building own framework/library? What I believe and experienced is each SPA JS Frameworks has its own set of rules and structure that has to be followed. If we want to have our own dyn