jQuery $.ajax( { async : false } ) 请求仍在异步触发？
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$.ajax( { async : false } ) request is still firing asynchronously?
提问by Galilyou
I got a little problem here guys. I'm trying to implement the following scenario:
我在这里遇到了一个小问题，伙计们。我正在尝试实现以下场景：
- A user opens the home page and sees a list of other users and clicks to add one to his friend list.
- I issue an Ajax request to a server resource to validate if the user is logged in, if so, I issue another ajax request to another server resource to actually add it to the user's friend list.
- 用户打开主页并看到其他用户的列表，然后单击将一个添加到他的朋友列表中。
- 我向服务器资源发出 Ajax 请求以验证用户是否已登录，如果是，则向另一个服务器资源发出另一个 ajax 请求以将其实际添加到用户的好友列表中。
Sounds simple? Here's what I've done: I created a function isLoggedInthat will issue the first request to the server in order to determine if the user is logged in. I issue this request using jQuery.ajaxmethod. Here's my function looks like:
听起来很简单？这是我所做的：我创建了一个函数isLoggedIn，该函数将向服务器发出第一个请求，以确定用户是否已登录。我使用jQuery.ajax方法发出此请求。这是我的功能：
function isLoggedIn() {
$.ajax({
async: "false",
type: "GET",
contentType: "application/json; charset=utf-8",
dataType: "json",
url: "/isloggedin",
success: function(jsonData) {
alert("jsonData =" + jsonData.LoggedIn);
return jsonData.LoggedIn;
}
});
}
The returned JSON is very simple, it looks like the following:
返回的JSON非常简单，如下所示：
{ LoggedIn: true } or { LoggedIn : false }
Now this method, actually works and displays the alert correctly: JsonData = trueif logged in, and JsonData = falseif not logged in.
Up to this point there's no problem, the problem occurs when I try to call this method: I call it like so:
现在这个方法，实际工作并正确显示警报：JsonData = true如果登录，JsonData = false如果没有登录。 到目前为止没有问题，当我尝试调用这个方法时出现问题：我这样调用它：
$(".friend_set .img").click(function() {
debugger;
if (isLoggedIn()) {
alert("alredy logged in");
trackAsync();
popupNum = 6;
}
else {
alert("not logged in"); //always displays this message.
popupNum = 1;
}
//centering with css
centerPopup(popupNum);
//load popup
loadPopup(popupNum);
return false;
});
Calling isLoggedInalways returns false, and it returns false before the ajax request finishes (because the messagejsonData = trueis displayed after the message "not logged in". I made sure that the request is **NOT** Asynchronous by statingasync: false`!
调用isLoggedIn总是返回false，它返回false before the ajax request finishes (because the messagejsonData = true is displayed after the message "not logged in". I made sure that the request is **NOT** Asynchronous by statingasync: false`！
Apparently it's still working asynchronously, though. What am I missing here guys?
不过，显然它仍在异步工作。伙计们，我在这里错过了什么？
回答by Roatin Marth
You need async:false, not async:"false". (i.e. pass boolean false, not string "false").
你需要async:false，不是async:"false"。（即传递 boolean false，而不是 string "false"）。
Edit:
also with async requests you need to return a value afterthe call to ajax, notinside your success handler:
编辑：对于异步请求，您需要在调用后返回一个值ajax，而不是在您的成功处理程序中：
function isLoggedIn() {
var isLoggedIn;
$.ajax({
async: false,
// ...
success: function(jsonData) {
isLoggedIn = jsonData.LoggedIn
}
});
return isLoggedIn
}
