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Single page application (SPA) using ext.js

what is spa?
Single page application are applications that fit in one page with rich and fluid user experiences like a desktop based applications.
Why is SPA?
All web based elements (html, CSS,javascript) are downloaded from the server on single page load and avoid the continuous page post back. i can explain what this mean. Suppose your web application is made of certain flow and it consists of 5 different pages. Each page need to get data from the user and save before moving to the next page. So when we navigate from one page to other it need to make a round trip to server to store the data in one page and get the data for the next page to display. but in spa we can avoid the continuous post backs. The whole page will not post back any time other than the first load. But it communicate to the server dynamically behind the scene and can achieve the same functionality.
Spa using ext.js
designing a SPA using ext.js is a challenging task if you are unaware about the ext.js framework or similar frameworks.
Ext JS is a javascript library from sencha and based on mvc-s architecture. Mvc-s means model-view-controller - store. If you are familiar with asp.net mvc or scrum we can simply compare ext.js mvc architecture the same way for javascript library. Model similar to the server side models, view consists of html, templates or widgets, controller consists of events and data transfer between the server side and client side. It also includes an additional cool feature called store. store encapsulate the client side cache data Model, say model is data row then store contains data table. Store got an option to auto sync with the data model. based on the need this auto sync option can be switched on/off. while sync'ing a store it will do the necessary dml (insert, update, delete) operations based on data.
Real time communication between the ext js and server side can be achieved by api controller (rest based service). api controller model and ext.js models have two way bindings. So it is easy to pass a model from the client side to the server. It can be configured using the routing configuration.
the client side dynamically communicate with the server side using ext.Ajax (rest api).
Data is retrieving from the server side as json objects. So it is easy to consume the responses from server side.
challenges
Some of the challenges are, how developers interpret the usage of technology, size of the application, time management Etc. If it is not handled properly this challenges can be the difference between the successful and scrapped project.

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