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参考

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The XMLHttpRequest Object


With the XMLHttpRequest object you can update parts of a web page, without reloading the whole page.


来试试吧 - 示例

A simple XMLHttpRequest example
Create a simple XMLHttpRequest, and retrieve data from a TXT file.

Retrieve header information with getAllResponseHeaders()
Retrieve header information of a resource (file).

Retrieve specific header information with getResponseHeader()
Retrieve specific header information of a resource (file).

Retrieve the content of an ASP file
How a web page can communicate with a web server while a user type characters in an input field.

Retrieve content from a database
How a web page can fetch information from a database with the XMLHttpRequest object.

Retrieve the content of an XML file
Create an XMLHttpRequest to retrieve data from an XML file and display the data in an HTML table.


The XMLHttpRequest Object

The XMLHttpRequest object is used to exchange data with a server behind the scenes.

The XMLHttpRequest object is the developers dream, because you can:

  • Update a web page without reloading the page
  • Request data from a server after the page has loaded
  • Receive data from a server after the page has loaded
  • Send data to a server in the background


XMLHttpRequest 对象方法

Method Description
abort() Cancels the current request
getAllResponseHeaders() Returns header information
getResponseHeader() Returns specific header information
open(method,url,async,uname,pswd) Specifies the type of request, the URL, if the request should be handled asynchronously or not, and other optional attributes of a request

method: the type of request: GET or POST
url: the location of the file on the server
async: true (asynchronous) or false (synchronous)
send(string) send(string) Sends the request off to the server.

string: Only used for POST requests
setRequestHeader() Adds a label/value pair to the header to be sent

XMLHttpRequest 对象属性

Property Description
onreadystatechange Stores a function (or the name of a function) to be called automatically each time the readyState property changes
readyState Holds the status of the XMLHttpRequest. Changes from 0 to 4:
0: request not initialized
1: server connection established
2: request received
3: processing request
4: request finished and response is ready
responseText Returns the response data as a string
responseXML Returns the response data as XML data
status Returns the status-number (e.g. "404" for "Not Found" or "200" for "OK")
statusText Returns the status-text (e.g. "Not Found" or "OK")



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