Shulou(Shulou.com)06/03 Report--

This article introduces the relevant knowledge of "how to understand AJAX development technology". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

AJAX (Asynchronous JavaScript and XML, Asynchronous JavaScript and XML), AJAX is not a new technology, its main purpose is for local page refresh. From the previous code development, readers can find that whenever a user makes a request to the server, even if only a little bit of local content is simply updated, the server will refresh the whole page and regenerate the code. In this way, the performance of the program will certainly be reduced, and if you use AJAX technology, you can achieve local content changes, without the overall page refresh, obviously the performance of processing is much higher than the former.

In AJAX, asynchronous requests and responses are mainly handled through the XMLHttpRequest object, which first appeared as an ActiveX component in IE 5 and was not widely used until 2005, and JavaScript must be used if you want to create a XMLHttpRequest object.

Properties of the XMLHttpRequest object

No.

Attribute

Description

one

Onreadystatechange

Specifies the action to be used when the readState state changes, which is generally used to specify a specific callback function

two

ReadyState

Returns the status of the current request, read-only

three

ResponseBody

Returns the body of the response message as a unsigned byte array, read-only

four

ResponseStream

Returns response information as an Ado Stream object, read-only

five

ResponseText

Receive data returned in plain text, read-only

six

ResponseXML

Receive data in the form of an XML document, read-only

seven

Status

Returns the http status code of the current request, read-only

eight

StatusText

Returns the response line status of the current request, read-only

Create a XMLHttpRequest object

The copy code is as follows:

Var xmlHttp; / / AJAX core object name

Function createXMLHttp () {/ / create XMLHttpRequest core object

If (window.XMLHttpRequest) {/ / determine the type of browser currently in use

XmlHttp = new XMLHttpRequest (); / / indicates that the browser used is the FireFox kernel

} else {/ / indicates that you are using a browser with IE kernel

XmlHttp = new ActiveXObject ("Microsoft.XMLHTTP")

}

}

There are five values for readState-one, which are:

The request is not made (before calling the open () function).

The request has been made but has not been issued (before calling the send () function).

The request has been made and is being processed (here you can usually get the content header from the response).

The request has been processed and information from the server is being received. Some data is usually available in the response, but the server has not yet completed the response.

The response is complete, and you can access the server response and use it.

Methods of XMLHttpRequest object

No.

Method

Description

one

Abort ()

Cancel the current request

two

GetAllResponseHeaders ()

Get all the HTTP header information

three

GetResponseHeader ()

Get a specified HTTP header information

four

Open ()

Create a HTTP request and specify the request mode, for example: GET request or POST request

five

Send ()

Send the created request to the server and receive the response message

six

SetRequestHeader ()

Sets the HTTP header information for a specified request

AJAX encapsulated code

Ajax.js

The copy code is as follows:

Function Ajax (recvType) {

Var aj=new Object ()

Aj.recvType=recvType? RecvType.toUpperCase (): 'HTML' / / HTML XML

Aj.targetUrl=''

Aj.sendString=''

Aj.resultHandle=null

Aj.createXMLHttpRequest=function () {

Var request=false

/ / the presence of XMLHttpRequest in the window object is non-IE, including (IE7,IE8)

If (window.XMLHttpRequest) {

Request=new XMLHttpRequest ()

If (request.overrideMimeType) {

Request.overrideMimeType ("text/xml")

}

/ / if the ActiveXObject attribute exists in the window object, it is IE

} else if (window.ActiveXObject) {

Var versions= ['Microsoft.XMLHTTP',' MSXML.XMLHTTP', 'Msxml2.XMLHTTP.7.0','Msxml2.XMLHTTP.6.0','Msxml2.XMLHTTP.5.0',' Msxml2.XMLHTTP.4.0', 'MSXML2.XMLHTTP.3.0',' MSXML2.XMLHTTP']

For (var item0; I

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