Shulou(Shulou.com)06/03 Report--

This article mainly introduces php how to use Ajax technology to detect user name, the article is very detailed, has a certain reference value, interested friends must read it!

1. Build the Ajax development framework with the following code

Var http_request = false;function createRequest (url) {/ / initialize the object and issue a XMLHttpRequest request http_request = false; if (window.XMLHttpRequest) {/ / Mozilla and other browsers http_request = new XMLHttpRequest (); if (http_request.overrideMimeType) {http_request.overrideMimeType ("text/xml") }} else if (window.ActiveXObject) {/ / IE browser try {http_request = new ActiveXObject ("Msxml2.XMLHTTP");} catch (e) {try {http_request = new ActiveXObject ("Microsoft.XMLHTTP") } catch (e) {}} if (! http_request) {alert ("cannot create XMLHTTP instance!"); return false;} http_request.onreadystatechange = alertContents / / specify response method http_request.open ("GET", url, true); / / issue HTTP request http_request.send (null) } function alertContents () {/ / process the information returned by the server if (http_request.readyState = = 4) {if (http_request.status = = 200) {alert (http_request.responseText);} else {alert ('error found on the page you requested');}

two。 Write the custom function checkname () of JavaScript to detect whether the user name is empty. If the user name is not empty, call the createRequest () method to send a request to detect the existence of the user name. The code is as follows:

Function checkname () {var username= form1.user.value; if (username== ") {window.alert (" Please enter a user name ");} else {createRequest ('action/checkname.php?username='+username+'&nocache='+new Date (). GetTime ());}}

3. Add "detect user name hyperlink" to the page

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