在Node.js上响应客户端的正确方式？

这是我第一次尝试构建服务器

我已经设置了一个服务器来处理联系人表单提交，其中还包括预定义的验证码字符串

当服务器接收到联系人表单时，如果captcha字符串是预期的，那么我希望它使用

response.end（JSON.stringify（parsedURL）），简单地用解析的联系人表单查询的JSON进行响应

如果验证码字符串错误，我希望服务器响应“说”验证码错误，以便客户端要求用户重试。但我不知道怎么做

在服务器上：

var httpServer = http.createServer(function (request, response)
{
    if (/\/contactform\?....../.test(request.url))
    {
        var parsedURL = url.parse(request.url, true);
        var name  = parsedURL.query.name;
        var email  = parsedURL.query.email;
        var subject  = parsedURL.query.subject;
        var enquiry  = parsedURL.query.enquiry;
        var captcha = parsedURL.query.captcha;

        if (captcha !== "testing")
        {
           // send a "bad" response to the client and include the message "bad captcha"
        }   

        else response.end(JSON.stringify(parsedURL.query));
    }
}).listen(8080);

$.ajax({
   url: "/contactform?..............",
   success: function(msg)
   {
      console.log(msg);
   },
   error: function(msg)
   {
      // the "bad captcha" response should be handled here right ?
      console.log(msg); // which should be equivalent to console.log("bad captcha");
   }
});

var httpServer = http.createServer(function (request, response)
{
    if (/\/contactform\?....../.test(request.url))
    {
        var parsedURL = url.parse(request.url, true);
        var name  = parsedURL.query.name;
        var email  = parsedURL.query.email;
        var subject  = parsedURL.query.subject;
        var enquiry  = parsedURL.query.enquiry;
        var captcha = parsedURL.query.captcha;
        var response = JSON.stringify(parsedURL.query);

        if (captcha !== "testing") response = "bad captcha";

        response.end(response);
    }
}).listen(8080);

$.ajax({
   url: "/contactform?..............",
   success: function(msg)
   {
      console.log(msg); // msg will either be the stringified object or "bad captcha"..
   }
}); 

在客户端上：

var httpServer = http.createServer(function (request, response)
{
    if (/\/contactform\?....../.test(request.url))
    {
        var parsedURL = url.parse(request.url, true);
        var name  = parsedURL.query.name;
        var email  = parsedURL.query.email;
        var subject  = parsedURL.query.subject;
        var enquiry  = parsedURL.query.enquiry;
        var captcha = parsedURL.query.captcha;

        if (captcha !== "testing")
        {
           // send a "bad" response to the client and include the message "bad captcha"
        }   

        else response.end(JSON.stringify(parsedURL.query));
    }
}).listen(8080);

$.ajax({
   url: "/contactform?..............",
   success: function(msg)
   {
      console.log(msg);
   },
   error: function(msg)
   {
      // the "bad captcha" response should be handled here right ?
      console.log(msg); // which should be equivalent to console.log("bad captcha");
   }
});

var httpServer = http.createServer(function (request, response)
{
    if (/\/contactform\?....../.test(request.url))
    {
        var parsedURL = url.parse(request.url, true);
        var name  = parsedURL.query.name;
        var email  = parsedURL.query.email;
        var subject  = parsedURL.query.subject;
        var enquiry  = parsedURL.query.enquiry;
        var captcha = parsedURL.query.captcha;
        var response = JSON.stringify(parsedURL.query);

        if (captcha !== "testing") response = "bad captcha";

        response.end(response);
    }
}).listen(8080);

$.ajax({
   url: "/contactform?..............",
   success: function(msg)
   {
      console.log(msg); // msg will either be the stringified object or "bad captcha"..
   }
}); 

当我使用
response.end（JSON.stringify（parsedURL））客户端（jQuery）认为“成功”

我应该如何从服务器响应，以便在客户端上执行ajax请求的“错误”部分

或者“错误”部分应该只处理服务器根本不响应的情况，即服务器端出现严重错误（如异常、真正的错误）的情况，而不是我在服务器上的评估没有预期结果的情况

我是否应该改为使用
response.end（…）在这两种情况下，如中所示：

在服务器上：

var httpServer = http.createServer(function (request, response)
{
    if (/\/contactform\?....../.test(request.url))
    {
        var parsedURL = url.parse(request.url, true);
        var name  = parsedURL.query.name;
        var email  = parsedURL.query.email;
        var subject  = parsedURL.query.subject;
        var enquiry  = parsedURL.query.enquiry;
        var captcha = parsedURL.query.captcha;

        if (captcha !== "testing")
        {
           // send a "bad" response to the client and include the message "bad captcha"
        }   

        else response.end(JSON.stringify(parsedURL.query));
    }
}).listen(8080);

$.ajax({
   url: "/contactform?..............",
   success: function(msg)
   {
      console.log(msg);
   },
   error: function(msg)
   {
      // the "bad captcha" response should be handled here right ?
      console.log(msg); // which should be equivalent to console.log("bad captcha");
   }
});

var httpServer = http.createServer(function (request, response)
{
    if (/\/contactform\?....../.test(request.url))
    {
        var parsedURL = url.parse(request.url, true);
        var name  = parsedURL.query.name;
        var email  = parsedURL.query.email;
        var subject  = parsedURL.query.subject;
        var enquiry  = parsedURL.query.enquiry;
        var captcha = parsedURL.query.captcha;
        var response = JSON.stringify(parsedURL.query);

        if (captcha !== "testing") response = "bad captcha";

        response.end(response);
    }
}).listen(8080);

$.ajax({
   url: "/contactform?..............",
   success: function(msg)
   {
      console.log(msg); // msg will either be the stringified object or "bad captcha"..
   }
}); 

在客户端上：

var httpServer = http.createServer(function (request, response)
{
    if (/\/contactform\?....../.test(request.url))
    {
        var parsedURL = url.parse(request.url, true);
        var name  = parsedURL.query.name;
        var email  = parsedURL.query.email;
        var subject  = parsedURL.query.subject;
        var enquiry  = parsedURL.query.enquiry;
        var captcha = parsedURL.query.captcha;

        if (captcha !== "testing")
        {
           // send a "bad" response to the client and include the message "bad captcha"
        }   

        else response.end(JSON.stringify(parsedURL.query));
    }
}).listen(8080);

$.ajax({
   url: "/contactform?..............",
   success: function(msg)
   {
      console.log(msg);
   },
   error: function(msg)
   {
      // the "bad captcha" response should be handled here right ?
      console.log(msg); // which should be equivalent to console.log("bad captcha");
   }
});

var httpServer = http.createServer(function (request, response)
{
    if (/\/contactform\?....../.test(request.url))
    {
        var parsedURL = url.parse(request.url, true);
        var name  = parsedURL.query.name;
        var email  = parsedURL.query.email;
        var subject  = parsedURL.query.subject;
        var enquiry  = parsedURL.query.enquiry;
        var captcha = parsedURL.query.captcha;
        var response = JSON.stringify(parsedURL.query);

        if (captcha !== "testing") response = "bad captcha";

        response.end(response);
    }
}).listen(8080);

$.ajax({
   url: "/contactform?..............",
   success: function(msg)
   {
      console.log(msg); // msg will either be the stringified object or "bad captcha"..
   }
}); 

换句话说，当服务器成功接收到请求，但服务器希望让客户端知道缺少了什么东西或其他什么东西时，服务器的响应是作为“错误”（即，由客户端ajax代码上的“错误”块处理）还是作为“成功”发送用适当的信息说明实际发生了什么？
我认为您需要做的是
设置响应的标题

以下是一个例子：

var body = 'Sorry!';
response.writeHead(404, {
  'Content-Length': body.length,
  'Content-Type': 'text/plain' });

更多信息，请参阅。
这个问题似乎在这里有答案：我看到了，但我没有使用express，我正在尝试先学习Node.js，然后再逐步升级。这个代码示例看起来是正确的，但是，我建议做两个轻微的修改：首先，使用403状态代码，而不是404。第二，保留原始的“错误验证码”正文内容，因为它向客户端描述了问题。为了回答更大的问题，通常认为在请求出现问题时返回成功的200响应是一种不好的做法。这只是一个简单的演示，您可以更改它以满足您的需要。我最终发送了这样的响应：
response.writeHead（403，{“Content Type”：“text/plain”}）；响应。结束（“错误验证码”）可以吗？顺便说一句，Troy，您建议的403代码会在浏览器控制台上显示一个错误（至少在Chrome上）。可以吗？我怎样才能避免呢？我相信这样的控制台错误会破坏IE，对吗？我认为403（禁止）状态在这种情况下似乎有点“苛刻”//太多了，不是吗？