Express return error without exiting in response

Question

I wrote a resource, to which a user can send data. If the data does not validate (validation returns false), I need to send an error 500 status code to the client, but the problem is, that when I use res.status(500), the program exits and I just want to cancel this request with an error to the client, not stopping the program...

function formHandler(req, res, next) {
    let isValid = validate(fields.token)
    if (!isValid) {
        res.status(500).send({ error: 'invalid!' })
    }

You might want a return after that line, or your code will continue and do stuff it's not meant to in error state. — Keith
– Keith, Commented Aug 15, 2018 at 10:35
Please add more code. I think res is not defined in that scope — Farhan Yaseen
– Farhan Yaseen, Commented Aug 15, 2018 at 10:38
@shopiaT Posted an example, ps. In a way I'm assuming this is the problem, the thing is you don't provide what code comes next, or even if your using an else block. Or more importantly any error message node might be giving.. — Keith
– Keith, Commented Aug 15, 2018 at 11:57

Keith · Accepted Answer · 2018-08-15 11:55:40Z

1

Please note, doing res.status(500).send({ error: 'invalid!' }) will not terminate the current function..

So ->

function formHandler(req, res, next) {
  let isValid = validate(fields.token)
  if (!isValid) {
    res.status(500).send({ error: 'invalid!' })
  }
  //so the code below will even run in invalid state
  res.send("this piece of code will run no matter what");

You could either call return, or use an else block.. eg.

function formHandler(req, res, next) {
  let isValid = validate(fields.token)
  if (!isValid) {
    res.status(500).send({ error: 'invalid!' });
    return;
  }
  res.send("this piece of code will only run if isValid");

Doing a second res.send again is most likely giving you the error, as the first res.send would have closed the connection..

answered Aug 15, 2018 at 11:55

Keith

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