What is Ajax?

Ajax is all called "Asynchronous JavaScript and XML" (Asynchronous JavaScript and XML), a Web development technology that creates interactive Web applications. It contains the following kinds of technologies organically:

Definition of Ajax (asynchronous JavaScript + XML): A representation based on the Web Standard (standards-based presentation) xhtml+css, using the DOM (Document Object Model) for dynamic display and interaction, use XML and XSLT for data exchange and related operations, use XMLHttpRequest for asynchronous data querying, retrieval, and use JavaScript to bind everything together.

Like DHTML or Lamp,ajax is not a single technology, but an organic use of a range of related technologies. In fact, some Ajax-based "derivation/Synthesis" (derivative/composite) technologies are emerging, such as "Aflax".

Ajax applications use a Web browser that supports the above technologies as a running platform. These browsers currently include: Mozilla, Firefox, Internet Explorer, Opera, Konqueror and Safari. However, Opera does not support XSL format objects, nor does it support XSLT.



The core of Ajax technology

Ajax has only the core of JavaScript, XMLHttpRequest, and Dom, and if the data format is XML, it can be added to the XML item (Ajax can be returned from the server side of the data is XML format, can be text and other formats).

In the old interaction, the user triggers an HTTP request to the server, the server processes it, returns a new HTHL page to the client, and every time the server processes a client-submitted request, the client can only wait, and even if it is only a small interaction, By simply getting a very simple piece of data from the server, you return a full HTML page, and the user wastes time and bandwidth each time to reread the entire page.

With Ajax, the user will quickly respond to a wait without a page overload (screen) from almost every operation it feels.

1, XMLHttpRequest

One of the biggest features of Ajax is the fact that you can transfer or read or write data to the server without refreshing the page (also known as no Refresh Update page), which is mainly thanks to the XMLHTTP component XMLHttpRequest object. This can be sent to the desktop application only with the server data level exchange, and do not refresh the interface every time without each time the data processing to the server to do, which is to reduce the burden of the server and accelerate the response speed, shorten the user waiting time.

The first applications xmlhttp Microsoft, IE (IE5), by allowing developers to extend their functionality within a Web page using XMLHTTP ActiveX components, developers can transfer data directly to or from the server without navigating from the current Web page. This feature is important because it helps to reduce the pain of stateless connections, and it also eliminates the need to download redundant HTML, thereby increasing the speed of the process. The response of Mozilla (Mozilla1.0 above and above NetScape7) is to create its own inherited XML proxy class: the XMLHttpRequest class. Konqueror (and Safari v1.2, also a khtml based browser) also supports XMLHttpRequest objects, and opera also supports v7.6x+ objects in later versions of XMLHttpRequest. For most cases, XMLHttpRequest objects are similar to XMLHTTP components, and methods and properties are similar, except that a small subset of properties are not supported.

2. JavaScript

JavaScript is a programming language that is used heavily in browsers, and he has been degraded to a bad language (he does use it rather boring) to be used to show off gadgets and pranks or tedious forms of verification. But the fact is that he is a real programming language, has its own standards and is widely supported in various browsers.

3, DOM

Document Object Model. A DOM is a set of APIs for use with HTML and XML files. It provides a structure statement of the file so that you can change the