ajax

 

function validate(field) {
          
if(window.XMLHttpRequest) {
            xmlHttp = new XMLHttpRequest();
        } else if (window.ActiveXObject) {
            xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
        }


        //alert(document.getElementById("userId").value);
        //alert(field.value);
        if (trim(field.value).length != 0) {
            //創建Ajax核心對象XMLHttpRequest
            createXMLHttpRequest();

            var url = "user_validate.jsp?userId=" + trim(field.value) + "&time=" + new Date().getTime();

            //設置請求方式爲GET，設置請求的URL，設置爲異步提交
            xmlHttp.open("GET", url, true);

            xmlHttp.onreadystatechange=function（）{

                
if (xmlHttp.readyState == 4) {
            //HTTP協議狀態爲成功
            if (xmlHttp.status == 200) {
                if (trim(xmlHttp.responseText) != "") {
                    //alert(xmlHttp.responseText);
                    document.getElementById("spanUserId").innerHTML = "<font color='red'>" + xmlHttp.responseText + "</font>"
                }else {
                    document.getElementById("spanUserId").innerHTML = "";
                }
            }else {
                alert("請求失敗，錯誤碼=" + xmlHttp.status);
            }
        }
                        }

            //將設置信息發送到Ajax引擎
            xmlHttp.send(null);
        } else {
            document.getElementById("spanUserId").innerHTML = "";
        }
    }