NodeJs express error middleware parsing

Question

I am trying to write a middleware to handle errors. But I cannot figure out how to send the correct format to my frontend. Below I am going to list all of my attempts in hopes of helping you help me.

Attempt 1

app.use(function(err, req, res, next) {
    const formatted = err;
    res.send(formatted)
});

result in postman

{ "code": 422 }

Attempt 2

app.use(function(err, req, res, next) {
    const formatted = `${err}`;
    res.send(formatted)
});

result (postman)

Error: Request returned error code: 422 and body: {"status":422,"title":"The display name: build_id has already been used on this product.","type":"https://developer.bigcommerce.com/api#api-status-codes","errors":{"display_name":"The display name: build_id has already been used on this product."}}

That is the data i want but i need it in json

Question Why is there more data revealed after string interpolation? How can i format it to json?

Possible duplicate of Proper way to set response status and JSON content in a REST API made with nodejs and express — Robert Moskal
– Robert Moskal, Commented Aug 15, 2018 at 18:28
The error your console.log() is not JSON it is a text. I think your error is related to bigcommerce as it returned in the message — Hello World
– Hello World, Commented Aug 15, 2018 at 19:15
why is it text? I know the API res (when i try in postman) returns json... turns it to text somewhere — Omar
– Omar, Commented Aug 15, 2018 at 19:17
Error: Request returned error code: 422 and body: {"status":422,"title":"The display name: build_id has already been used on this product.","type":"https://developer.bigcommerce.com/api#api-status-codes","errors":{"display_name":"The display name: build_id has already been used on this product."}} <-- This is actually a text/string. I don't know why !! On my understanding this is related to any of your external library which is causing it. I would suggest you to focus on the problem you are getting in console which is The display name: build_id has already been used on this product. — Hello World
– Hello World, Commented Aug 15, 2018 at 19:25

rickjerrity · Accepted Answer · 2018-08-15 18:34:15Z

0

You're probably looking for res.json(err) if I had to guess?

https://expressjs.com/en/api.html#res.json

EDIT: Full example:

app.use(function(err, req, res, next) {
    if (err) res.json(err)
});

edited Aug 15, 2018 at 18:34

answered Aug 15, 2018 at 18:26

rickjerrity

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3 Comments

Omar Over a year ago

That gives me json but not the full message... see attempt 5 (just added)

rickjerrity Over a year ago

You're still doing it wrong. I'll update my answer to be more clear.

Omar Over a year ago

That is not retuning the full message. >{"code": 422 }... Look at the difference between attempt one and two. That is the problem i need to figure out

Hello World · Accepted Answer · 2018-08-15 19:34:25Z

-1

You can do it in this way

app.use(function(err, req, res, next) {
    if (err) {
        res.json({
            status: "error",
            error: `${err}` // <-- edited
        });
    } else {
        next();
    }
});

edited Aug 15, 2018 at 19:34

answered Aug 15, 2018 at 18:32

Hello World

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3 Comments

Omar Over a year ago

If you look at attempt 1 there is only { "code": 422 } until attempt 2 where i did string interpolation. That is the same problem im having when i tried this. Only the code returns but not the message.

Hello World Over a year ago

@Omar can you explain it a bit more about the context like what request you are sending etc, this will help us find the problem.

Hello World Over a year ago

Did you tried sending the request via other platform or any browser??

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