下面的例子将演示网页如何通过 AJAX 从数据库读取信息： 请在下面的下拉列表中选择一个客户：
| <html><!DOCTYPE html> |
| <html> |
| <head> |
| <script> |
| function showCustomer(str) |
| { |
| var xmlhttp; |
| if (str=="") |
| { |
| document.getElementById("txtHint").innerHTML=""; |
| return; |
| } |
| if (window.XMLHttpRequest) |
| {// code for IE7+, Firefox, Chrome, Opera, Safari |
| xmlhttp=new XMLHttpRequest(); |
| } |
| else |
| {// code for IE6, IE5 |
| xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); |
| } |
| xmlhttp.onreadystatechange=function() |
| { |
| if (xmlhttp.readyState==4 && xmlhttp.status==200) |
| { |
| document.getElementById("txtHint").innerHTML=xmlhttp.responseText; |
| } |
| } |
| xmlhttp.open("GET","/try/ajax/getcustomer.php?q="+str,true); |
| xmlhttp.send(); |
| } |
| </script> |
| </head> |
| <body> |
| <form action=""> |
| <select name="customers" onchange="showCustomer(this.value)" style="font-family:Verdana, Arial, Helvetica, sans-serif;"> |
| <option value="APPLE">Apple Computer, Inc.</option> |
| <option value="BAIDU ">BAIDU, Inc</option> |
| <option value="Canon">Canon USA, Inc.</option> |
| <option value="Google">Google, Inc.</option> |
| <option value="Nokia">Nokia Corporation</option> |
| <option value="SONY">Sony Corporation of America</option> |
| </select> |
| </form> |
| <br> |
| <div id="txtHint">Customer info will be listed here...</div> |
| </body> |
| </html> |
当用户在上面的下拉列表中选择某个客户时，会执行名为 "showCustomer()" 的函数。该函数由 "onchange" 事件触发：
| function showCustomer(str) |
| { |
| var xmlhttp; |
| if (str=="") |
| { |
| document.getElementById("txtHint").innerHTML=""; |
| return; |
| } |
| if (window.XMLHttpRequest) |
| {// code for IE7+, Firefox, Chrome, Opera, Safari |
| xmlhttp=new XMLHttpRequest(); |
| } |
| else |
| {// code for IE6, IE5 |
| xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); |
| } |
| xmlhttp.onreadystatechange=function() |
| { |
| if (xmlhttp.readyState==4 && xmlhttp.status==200) |
| { |
| document.getElementById("txtHint").innerHTML=xmlhttp.responseText; |
| } |
| } |
| xmlhttp.open("GET","getcustomer.html?q="+str,true); |
| xmlhttp.send(); |
| } |
showCustomer() 函数执行以下任务：
由上面的 JavaScript 调用的服务器页面是 PHP 文件，名为 "getcustomer.php"。
用 PHP 编写服务器文件也很容易，或者用其他服务器语言。请看用 PHP 编写的相应的例子。
"getcustomer.php" 中的源代码负责对数据库进行查询，然后用 HTML 表格返回结果：
| <% |
| response.expires=-1 |
| sql="SELECT * FROM CUSTOMERS WHERE CUSTOMERID=" |
| sql=sql & "'" & request.querystring("q") & "'" |
| set conn=Server.CreateObject("ADODB.Connection") |
| conn.Provider="Microsoft.Jet.OLEDB.4.0" |
| conn.Open(Server.Mappath("/db/northwind.mdb")) |
| set rs=Server.CreateObject("ADODB.recordset") |
| rs.Open sql,conn |
| response.write("<table>") |
| do until rs.EOF |
| for each x in rs.Fields |
| response.write("<tr><td><b>" & x.name & "</b></td>") |
| response.write("<td>" & x.value & "</td></tr>") |
| next |
| rs.MoveNext |
| loop |
| response.write("</table>") |
| %> |
