AJAX is undoubtedly one of the hottest web development technologies in 2005. Of course, this credit cannot be separated from Google. I am just an ordinary developer and I don’t use AJAX very much. I will simply share my experience in using it. (This article assumes that the user already has basic Web development capabilities such as JavaScript, HTML, and CSS)
[Introduction to AJAX]
Ajax is a Web application development method that uses client-side scripts to exchange data with the Web server. Web pages can be dynamically updated without interrupting the interaction process and re-editing them. Using Ajax, users can create direct, highly available, richer, and more dynamic Web user interfaces that are close to native desktop applications.
Asynchronous JavaScript and XML (AJAX) is not a new technology, but uses several existing technologies - including Cascading Style Sheets (CSS), JavaScript, XHTML, XML and Extensible Style Language Transformations (XSLT) to develop look and action Web application software similar to desktop software.
[AJAX execution principle]
An Ajax interaction starts with a JavaScript object called XMLHttpRequest. As the name suggests, it allows a client-side script to perform HTTP requests and will parse an XML-formatted server response. The first step in Ajax processing is to create an XMLHttpRequest instance. Use the HTTP method (GET or POST) to handle the request and set the target URL to the XMLHttpRequest object.
When you send an HTTP request, you don't want the browser to hang and wait for a response from the server. Instead, you want to continue responding to the user's interface interactions through the page and process the server responses once they actually arrive. To accomplish this, you can register a callback function with XMLHttpRequest and dispatch the XMLHttpRequest request asynchronously. Control is immediately returned to the browser, and when the server response arrives, the callback function will be called.
[Practical Application of AJAX]
1. Initializing Ajax
Ajax actually calls the XMLHttpRequest object, so first we must call this object. We build a function to initialize Ajax:
/**
* Initialize an xmlhttp object
*/
functionInitAjax()
{
var ajax=false;
try {
ajax = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
ajax = new ActiveXObject("Microsoft.XMLHTTP");
} catch (E) {
ajax = false;
}
}
if (!ajax