用这个,

var url = req.headers.host + '/' + req.url;

你需要使用req.headers.host + req.url来构造它。当然，如果你是在不同的端口，你得到的想法;-)

用这个,

var url = req.headers.host + '/' + req.url;

var full_address = req.protocol + "://" + req.headers.host + req.originalUrl;

or

var full_address = req.protocol + "://" + req.headers.host + req.baseUrl;

我试着把所有数据都记录下来以备不时之需

然后我发现日志rawHeaders和发现所有的数据可用的url

我试了一下

app.post("/news-letter", (req,res) => {
    console.log(req.body);
    res.redirect(req.rawHeaders[33]);
})

const fullUrl = `${protocol}://${host}:${port}${url}`
      
    const responseString = `Full URL is: ${fullUrl}`;                       
    res.send(responseString);  
})