Javascript OnReadyStateChange作用域问题

我试图从函数中获取

New_Token

函数中

GetURL

的值，以便使用它。我想我的问题是

请求.onreadystatechange

行（尽管我不能确定）

GetURL

在函数外部未定义

var GetURL;
var request = new XMLHttpRequest();
var path="https://ops.epo.org/3.1/auth/accesstoken";

request.onreadystatechange= function() {New_Token(GetURL);};

var encodedData = window.btoa("key:secret"); //encode consumer key and secret key
request.open("POST", path, true);
request.setRequestHeader("Authorization", encodedData);
request.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
request.send('grant_type=client_credentials'); //send request to server, must include grant_type in payload or it won't work
alert(GetURL);

function New_Token(GetURL) {
    if (request.readyState == "4") //Request finished and response is ready
    {
        if (request.status == "200") {
            console.log(request.responseText);
            var TheResponse = JSON.parse(request.responseText);
            console.log(TheResponse);
            var TokenValue = TheResponse.access_token;
            console.log(TokenValue);
            GetURL = ("?access_token=" + TokenValue);
            console.log(GetURL); //this is the added string that needs to be concact. on to ALL OPS calls

            return(GetURL);
        }
        else {
             alert("Problem retrieving data");
            console.log(request.responseText);
        }
    }
}

试试这个

function New_Token(GetURL) {
    if (request.readyState == 4 || request.readyState == "complete") 
    {
        if (request.status == 200||request.status == 0) {
            console.log(request.responseText);
            var TheResponse = JSON.parse(request.responseText);
            console.log(TheResponse);
            var TokenValue = TheResponse.access_token;
            console.log(TokenValue);
            GetURL = ("?access_token=" + TokenValue);
            console.log(GetURL); //this is the added string that needs to be concact. on to ALL OPS calls
            return(GetURL);
        }
        else {
             alert("Problem retrieving data");
            console.log(request.responseText);
        }
    }
}

---

旧代码在New_Token函数中获取“GetURL”的正确值。我想弄清楚的是如何使GetURL全局化（或者至少返回GetURL以便我可以在函数外部访问它）。如果我遗漏了某些内容，我深表歉意，但我不相信您的代码会对该问题做出响应。我为误解您的问题深表歉意。当前发生了什么？GetURL的警报未定义。您的问题在于程序流。

request.send（…）

启动一个后台线程，该线程在发出

警报（…）

代码后终止。您应该将

警报（GetURL）

放在服务器响应您的

请求时执行的方法中。send（）