尝试/抓住jquery ajax请求 [英] Try/Catch with jquery ajax request

问题描述

我正在尝试建立一个提供ajax请求的Google Chrome扩展程序。类似于GMail Checker扩展。问题是当我使用jquery进行请求时，我输入错误的用户名/密码，它会默认地失败，错误回调函数被忽略。

如果我将ajax调用从background.html脚本（在开发人员窗口中看不到请求），到options.html脚本，我将获得一个对话框进行重新身份验证。如果我点击取消，那么jquery错误回调触发。

但是，在原始的模型扩展（再次，Gmail检查器）中，他们使用纯（非jquery）ajax调用一个try / catch，如果我输入错误的凭据，我会得到一个警报说尽可能多。

我尝试将整个jquery调用包装在一个try /如下所示：

  try {
 $ .ajax（{
 type：POST 
 url：someurl，
 contentType：text / xml，
 data：somedata，
 username：user，
 password：pass，
 success：函数（data，status，xhr）{
 alert（Hurray！）; 
}，
错误：function（xhr，status，error）{
 alert ！+ xhr.status）; 
}，
 dataType：xml
}）; 
} catch（e）{
 alert（你搞砸了！）; 
} 
  

但仍然没有。

是否因为异步而导致错误，或者Chrome不会将请求返回为错误，因为它要重新提示凭据？或者我不知道如何使用try / catch？

更新

这是一个非常纤薄的版本的模型代码如何执行请求：

  var req = new XMLHttpRequest（）; 
 req.onreadystatechange = function（）{
 try {
 if（req.readyState == 4）{
 //做一些结果的东西
} 
} 
 catch（ex）{
 alert（'解析响应错误'）; 
} 
} 
 try {
 req.send（data）; 
} 
 catch（ex）{
 alert（'请求发生错误'）; 
} 
  

解决方案

您有一个功能，每次请求完成后运行，无论发生什么。这应该解决问题：

  //存储全局变量，所以我们都可以很好的发挥。 
 
 //确保在AJAX调用之前重新设置为false，
 //或者只能工作一次！ 
 var weHaveSuccess = false; 
 
 $ .ajax（{
 type：POST，
 url：someurl，
 contentType：text / xml，
 data：somedata ，
 username：user，
 password：pass，
 success：function（data，status，xhr）{
 alert（Hurray！）; 
 weHaveSuccess = true; 
}，
 error：function（xhr，status，error）{
 alert（Error！+ xhr.status）; 
}，
 complete ：function（）{
 if（！weHaveSuccess）{
 alert（'您的用户名/密码似乎不正确！）; 
} 
}，
 dataType ：xml
}）; 
  

I am trying to build a Google Chrome extension that makes an ajax request. Something similar to the GMail Checker extension. The problem is that when I do the request using jquery, and I put in the wrong username/password, it fails silently, with the error callback function ignored.

If I move the ajax call out of the background.html script (where I can't see the requests in the developer window), to the options.html script, I get a dialog box to re-authenticate. If I hit cancel, THEN the jquery error callback fires.

But in the original model extension (again, the Gmail checker), they use plain (non-jquery) ajax calls with a try/catch, and if I put in the wrong credentials, I get an alert saying as much.

I tried wrapping the entire jquery call in a try/catch, like so:

try {
    $.ajax({
        type: "POST",
        url: someurl,
        contentType : "text/xml",
        data: somedata,
        username: user,
        password: pass,
        success: function(data,status,xhr){
            alert("Hurrah!");
        },
        error: function(xhr, status, error){
            alert("Error!" + xhr.status);
        },
        dataType: "xml"
    });
} catch(e) {
    alert("You messed something up!");
}

But still nothing.

Is the error due to it being asynchronous, or is Chrome not returning the request as an error since it wants to re-prompt for credentials? Or do I just not know how to use try/catch?

Update

Here is a very slimmed down version of how the model code does the request:

var req = new XMLHttpRequest();
req.onreadystatechange = function() {
    try {
        if ( req.readyState == 4 ) {
            //Do some stuff with results
        }
    }
    catch (ex) {
        alert('Error parsing response.');
    }
}
try {
    req.send (data);
}
catch (ex) {
    alert ('Something went wrong with the request.');
}

解决方案

Try something more like this, where you have a function that runs on every request once completed, regardless of what happens. This should solve the problem:

// Store a global var so we can all play nicely.

// Make sure this gets reset to false right before your AJAX call,
// or it will only work once!
var weHaveSuccess = false;

$.ajax({
    type: "POST",
    url: someurl,
    contentType : "text/xml",
    data: somedata,
    username: user,
    password: pass,
    success: function(data,status,xhr){
        alert("Hurrah!");
        weHaveSuccess = true;
    },
    error: function(xhr, status, error){
        alert("Error!" + xhr.status);
    },
    complete: function(){
        if(!weHaveSuccess){
             alert('Your username/password seems to be incorrect!');
        }
    },
    dataType: "xml"
});

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