异步Ajax调用工作不正常 [英] async-ajax call not working as expected

问题描述

设置：

我在做一个Ajax JSONP调用，这是工作的罚款。这样做的回调函数改变一个变量，myVaraible的价值。只是该呼叫后，有一些if-else逻辑其中工程上的myVaraible的值。

I am doing an ajax-jsonp call, which is working fine. The callback function of this changes value of a variable, "myVaraible". Just after the call, there is some if-else logic which works on the value of "myVaraible".

下面是code：

    <script>
        function myfunction() {
            $.ajax({
                url: myURL,
                dataType: "jsonp",
                jsonp : "jsonp",
                async: false,
                jsonpCallback: "jsonpCallbackFn"
            });
        }

        function jsonpCallbackFn(mydata) { 
            alert("inside jsonpCallbackFn");
            if(something) {
                // change value of a variable "myVariable";
            }
        }

        $(document).ready(function() {
            $("#preview_button").mouseover(function() {
                myfunction();

                alert("after myfunction");
                // do some if-else logic based upon the value of myVariable which is updated by the call to myfunction()
            });
        });
    </script>

的问题：

Ajax调用仍然悬而未决，控制转移到了的if-else块（有效地执行关于myVariable的旧/过时的值）。然后Ajax调用完成。总之，出了2 警告框，警报（之后MyFunction的）; 执行，然后再警报（内jsonpCallbackFn）;

The ajax call remains 'pending', the control moves to the if-else block (effectively executing on the old/stale value of myVariable). And then the ajax call completes. In short, out of the 2 alert boxes, alert("after myfunction"); executes first and then alert("inside jsonpCallbackFn");

正如你所看到的，我已经设置异步：假的，，不过貌似是不按预期工作。谁能告诉我，我究竟做错了什么？另外，我不知道我是否已经正确地解释整个方案，请让我知道是否需要任何更多的信息。

As you can see, I have already set async: false,, but looks like that is not working as expected. Can anyone tell me what am I doing wrong? Also, I am not sure if I have explained the entire scenario properly, please let me know if any more info is needed.

多谢了。

推荐答案

从 $就文档：

跨域请求和数据类型：JSONP请求不支持同步操作

Cross-domain requests and dataType: "jsonp" requests do not support synchronous operation

所以，你需要把任何依赖回调请求的结果。

So, you'll need to put anything that relies on the results of the request in the callback.

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