<script type="text/javascript">
             
function AddNumbers() 
{ 
    // Create an instance of the HTTP Request Object 
    var xmlHttp = new XMLHttpRequest(); 
 
    var value1 = document.getElementById("txtValue1").value; 
    var value2 = document.getElementById("txtValue2").value; 
 
    // Specify HTTP POST so that parameters can be passed in 
    // request body 
    xmlHttp.open("POST", "add.aspx", false); 
 
    // Send the parameters in CSV format 
    xmlHttp.send(value1 + "," + value2); 
 
    var result = document.getElementById("spanResult"); 
 
    // Use result of calculation from server 
    result.innerHTML = xmlHttp.responseText; 
}
             
</script> 
... 
<form> 
    <input id="txtValue1"/> 
    <input id="txtValue2"/> 
    <input onclick="AddNumbers();"type="button" value="Add"/> 
 
    <p>Result:</p> 
    <span id="spanResult"></span> 
</form> 

这个是原例子，跟你的要求一样：http://www.httpwatch.com/httpgallery/ajax/