AJAX Learning Record

2010-08-13  来源:本站原创  分类:Web  人气:149 

AJAX Learning Record

1. Definition:

XMLHTTP is a set in the javascript, vbscript, Jscript scripting languages such as sending or xml via http protocol and other data API

It is the biggest advantage is that we can update part of page

2. AJAX technology is used

javaScript: implementation client-side data transmission and interface updates are implemented ajax programming language;

XMLHttpRequest: browser, built-in used for asynchronous data transmission and reception of objects, is the core like AJAX;

Css + div: on the users, AJAX is the value of the user interface more friendly --- this of course, rely on css + div achieved;

DOM model: AJAX common technique is to use js dom component to respond to events or update;

Xml: XML is only a transport format of the data, often in ajax applications to xml format c / s between the exchange of data;

Html: The Needless to say, and data information displayed on the browser language.

3. AJAX three-step program

1. To take to the XMLHTTP object

function getRequestObject(){
                request = new XMLHttpRequest();
        }else if(window.ActiveXObject){
          request = new ActiveXObject("Msxml2.XMLHTTP");
          try{//IE Browser
                  request=new ActiveXObject("Microsoft.XMLHTTP")

      }//end try
                 window.alert(" Your browser does not support XMLHttpRequest, will not be able to use  AJAX.");

(2) set the callback function, the server sends back the information display to the development of components

// Will be returned by the server in the root update div
function processResult(){

        // Make sure the server answer ok, request objects processed
                alert(" The server returns the  :"+request.responseText);
                // Display to the specified component


(3) a request with the post

//AJAX Send a post request
function sendRequest(){
     // Get  XMLHttpRequest
    // To bind a callback method
   // Send a request
    request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
     var username=document.getElementById("username").value;


To get a request

function sendRequest(){
     // Get  XMLHttpRequest
    // To bind a callback method
   // Send a request  

     var username=document.getElementById("username").value;

The character set encoding issues will exist, will enter the Chinese will be garbled.

4. To solve hair problems and methods

1. Send a request garbled problems

(1) method to send the request to get it, I have not found a solution.

(2) send a request to post, long as you write

request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");

Words, the problem will not be garbled, and it is utf-8 default encoding format, so the server side not to set the encoding of the request

It is worth noting that if the request method to post, if it does not write the above sentence, to the server's value is null

And to pay attention to the order of the problem, first write



request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");

Otherwise, the value is null

2.js program does not error, so it is that error detection, however, any program is wrong, the program will break at that, not the smooth implementation of the results you want, so we should pay attention to write start writing test statement

3. Why do we open the third parameter set to true?

Specifies whether the asynchronous request processing.

True said the script will send () method after the continue without waiting for a response from the server.

onreadystatechange event to make the code complicated. But this is not the case the server response to prevent the code to stop the most secure method.

By this parameter is set to "false", can save the extra onreadystatechange code. If the request fails if the rest of the code execution does not matter, you can use this parameter.

4. Call the callback method, the method name can not be bracketed. Such as:


processResult not write parentheses, or AJAX can not run correctly

5. When the code in the implementation of the

var descs=request.responseXML.getElementsByTagName("desc");

This sentence does not continue on the implementation of the time, the server sends the xml file was wrong, or the

response.setContentType("text/xml; charset=gbk");

The text / xml written in other formats.

5. Uploaded file in the five classic example AJAX

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