Ajax表单提交乱码

Ajax表单提交数据出现乱码和解决办法
   //要传递的参数
   var queryString = "firstName=" + firstName + "&lastName=" + lastName
                          + "&birthday=" + birthday;    function 
//GET方式提交   
doRequestUsingGET() {   
         createXMLHttpRequest();   
        var url = "GetAndPostExample?" + queryString + "&timeStamp="  
                           + new Date().getTime();   
         xmlHttp.onreadystatechange = handleStateChange;   
         xmlHttp.open("GET", url, true);   
         xmlHttp.send(null);   
}   
  
//POST方式提交   
function doRequestUsingPOST() {   
         createXMLHttpRequest();   
        var url = "GetAndPostExample?timeStamp=" + new Date().getTime();   
         xmlHttp.open("POST", url, true);   
         xmlHttp.onreadystatechange = handleStateChange;   
         xmlHttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");   
         xmlHttp.send(queryString);   
}  
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