Ajax sends and receives requests. Ajax sends and receives requests.

Ajax sends and receives requests. Ajax sends and receives requests.

First, Ajax is widely used to submit data without refreshing new pages !!

Basically, Ajax can receive the information that the browser can receive. ex: String, html Tag, css Tag, xml format content, json format content, and so on .....

<Script> // IE browser if (ActiveXObject) {// the latest version of Microsoft AJAX var ajax = new ActiveXObject ("Msxm12.XMLHTTP. 6.0 ");} else {// mainstream browser var ajax = new XMLHttpRequest ();} // create an HTTP request // open (method, url, asynchronous, user, password ); // method: Request method (post, get) // url: request address (the address of the specific data to be received) // asynchronous: synchronous or asynchronous request (true is asynchronous, "false" indicates synchronization. The default value is "true". You can leave it empty. // user :( specify the request username, but do not enter it) // password :( specify the request password, or leave it empty) ajax. open ('get', 'url'); ajax. onreadystatechange = function () {if (ajax. readyState = 4) & (ajax. status) = 200) {alert (ajax. responseText); // returned data content} else {alert ('request failed');} // send the request. The content is the content to be sent, if not, enter null send (content); // If a post request is used, set the HTTP header ajax before sending. setRequestHeader ("Content-Type", "application/x-www-form-urlencoded"); </script>

The onreadystatechange event of ajax can receive up to four changed states.

Returned status value of readystate:

0 (not initialized) the object has been created

1 (initialization) The open method has been called

2 (send data) The send method has been called

3 (in data transmission) Some data has been returned

4. The request is completed successfully.

The above is a simple Ajax request principle and I hope it will be helpful for your learning.

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