javascript - onreadystatechange 函数在 AJAX 中不起作用

Question

就 XMLHttpRequest() 对象而言，没问题，问题出在 onreadystatechange 例如，如果我这样放置我的代码，它会完美运行。

function process(){
    var xmlHttp = new XMLHttpRequest();

    if(xmlHttp){
        xmlHttp.onreadystatechange = function(){
            theD = document.getElementById("theD");
            if(xmlHttp.readyState == 1){
                theD.innerHTML += "Status 1: Server connection established ! <br/>";
            }
            else if(xmlHttp.readyState == 2){
                theD.innerHTML += "Status 2: Request recieved ! <br/>";
            }
            else if(xmlHttp.readyState == 3){
                theD.innerHTML += "Status 3: Processing Request ! <br/>";
            }
            else if(xmlHttp.readyState == 4){

                if(xmlHttp.status == 200){
                    var text = xmlHttp.responseText;
                    theD.innerHTML += "Status 4: Processing Request ! <br/>";
                    theD.innerHTML += text;
                }
                else{
                    alert("Something is wrong !");
                }
            }
        };
        xmlHttp.open("GET", "hello.txt", true);
        xmlHttp.send();
    }
}

但如果我创建一个函数 handleServerResponse()

function handleServerResponse(){
    theD = document.getElementById("theD");
    if(xmlHttp.readyState == 1){
        theD.innerHTML += "Status 1: Server connection established ! <br/>";
    }
    else if(xmlHttp.readyState == 2){
        theD.innerHTML += "Status 2: Request recieved ! <br/>";
    }
    else if(xmlHttp.readyState == 3){
        theD.innerHTML += "Status 3: Processing Request ! <br/>";
    }
    else if(xmlHttp.readyState == 4){

        if(xmlHttp.status == 200){
            var text = xmlHttp.responseText;
            theD.innerHTML += "Status 4: Processing Request ! <br/>";
            theD.innerHTML += text;
        }
        else{
            alert("Something is wrong !");
        }
    }
}

并称它为

xmlHttp.onreadystatechange = handleServerResponse();

这是行不通的。如有错误请指出。

Answer 1

尝试使用

xmlHttp.onreadystatechange = handleServerResponse;

注意删除的括号。