发送后无法设置headers。在节点中

Question

I am not getting why error Can't set headers after they are sent. pops up. Here is my error.

   _http_outgoing.js:494
        throw new Error('Can\'t set headers after they are sent.');
        ^

Error: Can't set headers after they are sent.
    at validateHeader (_http_outgoing.js:494:11)
    at ServerResponse.setHeader (_http_outgoing.js:501:3)
    at ServerResponse.header (D:\trraks\node_modules\express\lib\response.js:767:10)
    at ServerResponse.send (D:\trraks\node_modules\express\lib\response.js:170:12)
    at ServerResponse.json (D:\trraks\node_modules\express\lib\response.js:267:15)
    at IncomingMessage.<anonymous> (D:\trraks\app\routes\api.js:58:17)
    at emitOne (events.js:116:13)
    at IncomingMessage.emit (events.js:211:7)
    at IncomingMessage.Readable.read (_stream_readable.js:475:10)
    at flow (_stream_readable.js:846:34)
    at resume_ (_stream_readable.js:828:3)
    at _combinedTickCallback (internal/process/next_tick.js:138:11)
    at process._tickCallback (internal/process/next_tick.js:180:9)

我正在尝试在用户手机号码上发送 OTP 这里是所有声明

var code = user.CODE;
var msg =urlencode("Dear User,\nVerify your mobile number.\nYour verification code is "+ code);
var number=user.MOBILENO;
var data ='username='+username+'&hash='+hash+'&sender='+sender+'&numbers='+number+'&message='+msg
                var options = {
                host: 'api.textlocal.in',
                path: '/send?'+data
                };

                    callback = function(response) 
                    {

                          response.on('data', function (chunk) 
                          {
                                res.json({ success: true, messege: "Messege send on given number"});

                          });

                    }

在运行第一次编码后一切正常，但第二次，它显示上述错误。

http.request(options, callback).end();

以上行发送消息。

Verifyotp.GetMobileNumber(user.MOBILENO,function(err,mobexits){
                            if (!mobexits) {
                                // new number with new OTP
                                    user.save(function(err){
                                    if(err){
                                        // console.log(err);
                                        res.json({success:false, messege:"Something went wrong while trying to send otp"});
                                    }else{

                                        res.json({success:true, messege: "OTP sent on given mobile number new"});
                                        http.request(options, callback).end();
                                    }
                                })
                            }else{
                                // updating new OTP on old number
                                Verifyotp.UpdateOtp(user.MOBILENO,user.CODE,function(err,update){
                                    if (!update) {
                                        res.json({success:false, messege: "something went wrong while sending OTP"})
                                    }else{
                                        res.json({success:true, messege: "OTP sent on given mobile number updated"});
                                        http.request(options, callback).end();

                                    }
                                });

                            }
                        });

这是我的 mongooseSchema :

var User =  module.exports = mongoose.model('verifydata',UserSchema);

module.exports.GetMobileNumber = function(mobileno,callback){
    const query={MOBILENO:mobileno};
    User.findOne(query,callback);
}

module.exports.UpdateOtp = function(mobilenumber,code,callback){
    const query = {MOBILENO: mobilenumber};
User.findOneAndUpdate(query, { CODE: code }, callback);
}

帮助我的朋友们...我尝试了一切，但没有任何效果。提前致谢

Answer 1

免责声明，我没有彻底检查您的代码，我发现的一个建议是，在理想情况下，您不要在一个函数中多次使用 "res.send" 或相关代码。当您尝试多次发送响应时，通常会抛出该错误。因此，为了安全起见，请尝试仅使用 res 一次，或最多两次（首先用于发送响应，其次用于抛出错误）

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