Ajax JavaScript Learning Summary

Ajax, is the asynchronous request, specifically want to update a part of the page, no need to reload the entire page, as long as the sending request to update the local page.

Ajax, not new language, just a technology

The use of Ajax relies on XMLHttpRequest objects, and the "members" commonly used in objects include: Open, Send,responsetext,onreadystatechange

Create Xhr object: var xmlrequest = new XMLHttpRequest ();

xhr Send request: Xmlrequest.open ("method", "url", True/false);

Xmlrequest.send ([string]);

parameters in open:

1. Method:get/post, and select one to indicate the method used when sending
2. URL: The location of the file on the server, or the path
3. The third argument, if true, is asynchronous, and vice versa is synchronous

parameters in Send:

1. String can only be used when the POST request, the GET request to transfer more content to add in the URL

XHR Response: When transmitting a string, use: responsetext eg:var tmptext = Xmlrequest.responsetext;

The transport XML format is, using: responsexml eg:var tmpxml = xmlrequest.responsexml;

onReadyStateChange: Use this to store the function to be executed when the data is returned; Here are two volumes: one is readyState and the other is status. Whenever the value of readystate changes, it is called

onReadyStateChange this function.

value of readystate:0-Request not initialized

The server connection has been established

2-Request received

3-In Request processing

4-The request is complete and the response is ready

Status value:"404": Page not Found

"$": OK

Examples from the world-class:

Xmlhttp.onreadystatechange=function () {      if (xmlhttp.readystatexmlhttp.status==200)        {            document.getElementById ("mydiv"). innerhtml=xmlhttp.responsetext;        } }

Use a callback function instead of onreadystatechange, written like this:

function Loadxmldoc () {.... AJAX script goes here ...} </script>

function MyFunction () {     Loadxmldoc ("Ajax_info.txt", function ()     {            if (xmlhttp.readystate==4 && xmlhttp.status==200)              {                 document.getElementById ("mydiv"). Innerhtml=xmlhttp.responsetext;              }     );}

　　

Ajax JavaScript Learning Summary