Slide Web thế hệ mới - Chapter 2.3 ajax

What is AJAX ? Asynchronous Javascript and XML. Not a stand-alone language or technology. It is a technique that combines a set of known technologies in order to create faster and more user friendly web pages. It is a client side technology. Purpose of AJAX Prevents unnecessary reloading of a page. When we submit a form, although most of the page remains the same, whole page is reloaded from the server. This causes very long waiting times and waste of bandwidth. AJAX aims at loading only the necessary innformation, and making only the necessary changes on the current page without reloading the whole page. Technologies Used AJAX uses: Javascript (for altering the page) XML (for information exchange) ASP or JSP (server side) Simple Processing AJAX is based on Javascript, and the main functionality is to access the web server inside the Javascript code. We access to the server using special objects; we send data and retrieve data. When user initiates an event, a javascript function is called which accesses server using the objects. The received information is shown to the user by means of the Javascript’s functions. Example We want to input data into a textbox. We want the textbox to have intellisense property; guess entries according to input. http://www.w3schools.com/ajax/ajax_example.asp Only the ‘span’ part of the html code is changed. Data Exchange in AJAX In AJAX: Example(2) Another example: http://www.w3schools.com/ajax/ajax_database.asp Therefore, by using AJAX, unnecessary exchange of data is prevented, web pages become: More interactive Faster More user friendly History of AJAX Starts with web pages Static web pages Static html page is loaded No interaction with user Dynamic web pages Html page is generated dynamically Interaction with user Becomes slower as functionality increases Speed becomes untolerable, so AJAX has been born Alternative Technologies Not a technology

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