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Event Handling Programming with AJAX
By: Courtney Ball and Brian Robbins
Traditional AJAX AJAX – Asynchronous JavaScript and
XML
Traditional AJAX
Ajax is used to develop fast dynamic web applications
Allows web pages to be updated asynchronously by transferring data server side behind the scenes
Ajax is not a programming language itself but uses various web development techniques such as JavaScript, PHP, HTML, CSS and XML
Traditional AJAX
Ajax uses HTTP requests to serve as the connection between the server and the user
Data is sent to the server, processed and immediately sent back to client side
Traditional Ajax
Event Driven AJAX Similar execution to traditional Ajax but
uses an XMLHttpRequest object Instead of using a continuous HTTP
connection, after a request is sent, the request is terminated, so there are new requests after each response
Event Driven AJAX
Our Project
Using HTML, JavaScript and PHP, we are creating a simple web page that displays 5 options of colors in which the user can change the background to their desired color
User Interface
Screen Shots
Coding Examples
JavaScript for UI
//Function that is called by the forms in javascript
function blue() { document.bgColor = "blue"; }
//Form for calling a specific color<input type="button" value="BLUE" onClick= "blue()" />
function blue() { var xhr; //try and catch block for particular web browser
try { xhr = new ActiveXObject('Msxml2.XMLHTTP');
} catch (e) { try { xhr = new ActiveXObject('Microsoft.XMLHTTP'); } catch (e2) { try { xhr = new XMLHttpRequest(); //Instantiates new XmlHttpRequest Object }
catch (e3) { xhr = false; } } }
xhr.onreadystatechange = function() {
if(xhr.readyState == 4) {
if(xhr.status == 200) document.bgColor = "blue"; else document.ajax.dyn="Error code " ; }
};
XMLHttpRequest object
Conclusion
Ajax is effective for fast dynamic web browsing, it is commonly used so that a user does not have to refresh the we browser to acquire new information
Conclusion
Ajax is commonly seen in the popular social network facebook
It is also used in eCommerce websites such as eBay
Most recent it is seen in Youtube
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