Details about how to use AJAX and how to use AJAX

Source: Internet
Author: User

Details about how to use AJAX and how to use AJAX

As asynchronous transmission, AJAX is very convenient and useful for local refreshing!

First, there are four steps to use AJAX:

1. Create an AJAX object

var xmlHttp = new XMLHttpRequest();

2. Establish a connection ('submission method ', 'url address ')

xmlHttp.open('get','./AJAX_XML.xml');

3. Determine the ajax preparation status and status code

xmlHttp.onreadystatechange = function(){    if (xmlHttp.readyState==4 && xmlHttp.status==200) {  }}

4. Send a request

XmlHttp. send (null); // The get method parameter is null, THE post method, and the parameter is the submitted parameter.

The user name is submitted asynchronously. (After the user name is entered, the user name is submitted asynchronously to the background for determination. The foreground immediately prompts whether the user name has been registered and does not need to be submitted !)

Submit in GET Mode

Xx.html

<Script type = "text/javascript"> window. onload = function () {document. getElementById ('username '). onblur = function () {var name = document. getElementById ('username '). value; var req = new XMLHttpRequest (); req. open ('get', '4-demo. php? Name = '+ name); req. onreadystatechange = function () {if (req. readyState = 4 & req. status = 200) {alert (req. responseText) ;}} req. send (null); // If the send () method does not contain data, write null }}</script>

User name:<input type="text" name="" id="username">

Xx. php

<?phpprint_r($_GET);?> 

1. IE does not support Chinese Characters

2. =, & is confused with the keyword of the request string.

POST submission

Xx.html

<script type="text/javascript">window.onload=function(){  document.getElementById('username').onblur=function(){    var name=document.getElementById('username').value;    name=encodeURIComponent(name);    var req=new XMLHttpRequest();    req.open('post','5-demo.php?age='+20);    req.onreadystatechange=function(){      if(req.readyState==4 && req.status==200){        alert(req.responseText);      }    }  req.setRequestHeader('Content-Type','application/x-www-form-urlencoded');    req.send('name='+name);    }}</script>

User name:<input type="text" name="" id="username">

Xx. php

<?phpprint_r($_POST);print_r($_GET);?> 

1. send data through send ()

2. You must set setRequestHeader () to convert the passed parameters to XML format.

3. post submission can directly submit Chinese characters without Transcoding

4. The characters in the post request will also be confused with the &, = characters in the URL. Therefore, we recommend that you use encodeURIComponent () encoding.

5. GET submission can be performed at the same time as POST submission.

SolutionIE does not support Chinese =, & obfuscation with the keyword of the request stringProblem

In js, use encodeURIComponent () to encode it.

Window. onload = function () {document. getElementById ('username '). onblur = function () {var name = document. getElementById ('username '). value; name = encodeURIComponent (name); // encode var req = new XMLHttpRequest (); req. open ('get', '4-demo. php? Name = '+ name); req. onreadystatechange = function () {if (req. readyState = 4 & req. status = 200) {alert (req. responseText) ;}} req. send (null); // If the send () method does not contain data, write null }}

1. req. responseText: gets the returned string.

2. req. responseXML: Get the returned data according to the DOM Structure

Note the difference between the post and get submission methods!

The above is all the content of this article. I hope this article will help you in your study or work. I also hope to provide more support to the customer's home!

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.