XMLHTTPRequest 响应在标头中不包含 Location 字段

问题描述

我试图修改 adblockplus 代码以进行测试.我正在修改代码以在 URL 上发送 http get 请求并从响应中获取最终 URL.我尝试使用下面的代码，但响应不包含标头响应中的 Location 字段.我在 Firefox 扩展中这样做，所以我认为跨域请求不会有任何问题.为什么我无法从响应中获取 Location 字段?有没有更好的方法来完成这项任务?

I was trying to modify the adblockplus code for testing purpose. I was modifying the code to send a http get request on a URL and get the final URL from the response. I tried using the below code, but the response doesn't contain the Location field in the header response. I am doing this within a firefox-extension, so I dont think cross-domain request would be any issue. Why is it that I am not able to fetch the Location field from the response? Is there a better way to accomplish this task ?

输入网址- http://netspiderads3.indiatimes.com/ads.dll/clickthrough?msid=17796167&cid=3224&slotid=1203&nsRndNo=817685688

预期输出-http://www.mensxp.com/

实际输出-位置:空

这是我正在使用的代码-

Here is the code I am using-

function geturl(url){
let req= Cc["@mozilla.org/xmlextras/xmlhttprequest;1"].createInstance(Ci.nsIXMLHttpRequest);
req.open("GET", url);
req.overrideMimeType("text/plain");
req.send(null);
req.onreadystatechange = function() {
if (req.readyState == 4) 
{ if (req.status == 200) 
  { try 
    {
       location = req.getResponseHeader("Location");
       console.log("Location is: " + location);
    }
    catch(e){
    console.log("Error reading the response: " + e.toString());
  }
 }
}

解决方案-

我终于找到了解决方案.我没有得到最终的回应.所以我将重定向限制设置为 0，现在我可以在标题中获取 Location 字段.这是我添加到代码中的内容-

I finally found the solution for this. I was not getting the final response. So I set the redirection limit to 0, now I can get the Location field in the header. Here is what I added to my code-

if (request.channel instanceof Ci.nsIHttpChannel)
    request.channel.redirectionLimit = 0;

推荐答案

其实你要检查readyState == 2，也就是HEADERS_RECEIVED状态

Actually you have to check for readyState == 2, that is HEADERS_RECEIVED state

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