Getting Can't set headers after they are sent after res.send() in express js

Question

I am getting this error every time a do a POST request. My code is:

records.post('/addNewRecord',
[
    check('applicant_name').not().isEmpty().withMessage('Applicant name cannot be empty').trim().escape(),
    check('applicant_type').not().isEmpty().withMessage('Please select an applicant type').trim().escape(),
    check('applicant_address').not().isEmpty().withMessage('Applicant address cannot be empty').trim().escape(),
    check('applicant_contact').not().isEmpty().withMessage('Applicant contact cannot be empty').trim().escape(),
    check('building_name').not().isEmpty().withMessage('Building name cannot be empty').trim().escape(),
    check('building_address').not().isEmpty().withMessage('Building Address cannot be empty').trim().escape(),
    check('building_area').not().isEmpty().withMessage('Building Area cannot be empty').trim().escape(),
    check('file_number').not().isEmpty().withMessage('File number cannot be empty').trim().escape(),
    check('remark').trim().escape()
],
function(req, res) {
    const errors = validationResult(req)
    if (!errors.isEmpty()) {
        res.status(200).send({message: errors.array(), saved : false})
    }
    const fileRecordData = {
        "APPLICANT_NAME": req.body.applicant_name,
        "APPLICANT_TYPE": req.body.applicant_type,
        "APPLICANT_ADDRESS": req.body.applicant_address,
        "APPLICANT_CONTACT": req.body.applicant_contact,
        "BUILDING_NAME": req.body.building_name,
        "BUILDING_ADDRESS": req.body.building_address,
        "BUILDING_AREA": req.body.building_area,
        "FILE_NUMBER": req.body.file_number,
        "REMARK": req.body.remark,
    }
    connection.query(`INSERT INTO ${process.env.FILE_RECORD_TBL} SET ?`, fileRecordData, function(err, results, fields) {
        if (err) {
            res.status(200).send({message : err, saved : false})
        }
        res.status(200).send({message : 'Record saved successfully', saved : true})
    })
}

)

I get this error every time irrespective of which res.status() gets called depending on the condition.

I have seen other answers on SO but and I have applied them but the problem doesn't seem to go away.

can you post the full route? maybe other code is sending something first. post the app js(atleast the relevant part) — Aritra Chakraborty, Aug 07 '18 at 05:59
@AritraChakraborty updated the question with full route please check — Dean Ambrose, Aug 07 '18 at 06:00

abdulbarik · Accepted Answer · 2018-08-07T06:10:19.783

You are sending response two times that's why getting this error.

And as per this code base you are getting error that's why your error block is calling with outer response

Try this:

    records.post('/addNewRecord', [
    check('applicant_name').not().isEmpty().withMessage('Applicant name cannot be empty').trim().escape(),
    check('applicant_type').not().isEmpty().withMessage('Please select an applicant type').trim().escape(),
    check('applicant_address').not().isEmpty().withMessage('Applicant address cannot be empty').trim().escape(),
    check('applicant_contact').not().isEmpty().withMessage('Applicant contact cannot be empty').trim().escape(),
    check('building_name').not().isEmpty().withMessage('Building name cannot be empty').trim().escape(),
    check('building_address').not().isEmpty().withMessage('Building Address cannot be empty').trim().escape(),
    check('building_area').not().isEmpty().withMessage('Building Area cannot be empty').trim().escape(),
    check('file_number').not().isEmpty().withMessage('File number cannot be empty').trim().escape(),
    check('remark').trim().escape()
  ],
  function (req, res) {
    const errors = validationResult(req)
    if (!errors.isEmpty()) {
        // break the function execution if condition is true
     return  res.status(200).send({
        message: errors.array(),
        saved: false
      });
    }
    const fileRecordData = {
      "APPLICANT_NAME": req.body.applicant_name,
      "APPLICANT_TYPE": req.body.applicant_type,
      "APPLICANT_ADDRESS": req.body.applicant_address,
      "APPLICANT_CONTACT": req.body.applicant_contact,
      "BUILDING_NAME": req.body.building_name,
      "BUILDING_ADDRESS": req.body.building_address,
      "BUILDING_AREA": req.body.building_area,
      "FILE_NUMBER": req.body.file_number,
      "REMARK": req.body.remark,
    }
    connection.query(`INSERT INTO ${process.env.FILE_RECORD_TBL} SET ?`, fileRecordData, function (err, results, fields) {
      if (err) {
          // break the callback execution if getting error
        return res.status(200).send({
          message: err,
          saved: false
        })
      }
      res.status(200).send({
        message: 'Record saved successfully',
        saved: true
      });
    })
  });

this works with return but is using return mandatory with res.send() ?? — Dean Ambrose, Aug 07 '18 at 06:05
how of handle it properly?....the first part of your answer doesn't work for me either — Dean Ambrose, Aug 07 '18 at 06:07
the main purpose is that it should not send response more than one times, and now its up to you how you want to handle — abdulbarik, Aug 07 '18 at 06:07
you mean even if they are in if-else block they should be send only once in a route?........can you show me how to do it without return — Dean Ambrose, Aug 07 '18 at 06:08
I have updated the answer and it should work in all scenario, BTW you need to take care the control flow of execution — abdulbarik, Aug 07 '18 at 06:11
thanks.... "take care of the control flow of execution" what do you mean by this can you please ellaborate — Dean Ambrose, Aug 07 '18 at 06:14
mean you need to understand the control flow where use `if else` where use `return` etc.. then you'll never stuck in such type of error — abdulbarik, Aug 07 '18 at 06:15
should I use res.write() and then a final res.end() in the end to do this without return — Dean Ambrose, Aug 07 '18 at 06:17
https://stackoverflow.com/questions/44692048/what-is-the-difference-between-res-send-and-res-write-in-express hope you'll get your answer — abdulbarik, Aug 07 '18 at 06:20

Getting Can't set headers after they are sent after res.send() in express js

1 Answers1