Question 117204 in Mongodb Question posted in
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Mongodb – API Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client

I am having an error when people register or try to login, it throws me the following error, but it happens sometimes,
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my code is the following
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2

Answers


  1. 0

    res.send can only be called once. In the bcrypt.compare callback, res.send is called twice (for both statuses 201 and 200). Also, you must use a return statement after res.send or return res.send. This is because the code continues after executing the function.

    You can also:

    • Change the status code for a false result to 400 – best practice
    • Remove the 500 as it is never reached.

    I have applied these changes to my code below.

    Fixed code:

    ...
if (!result) {
    return res.status(400).json({
            error: "User or password invalid",
        })
    }

    const userForToken = {
        id: users._id,
        name: users.name,
    }

    const token = jwt.sign(userForToken, process.env.SECRET)

    res.status(200).send({
        name: users.name,
        email: users.email,
        token,
        result: true,
        id: users._id,
    })
}
...
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  2. 0

    res.status().send() doesn’t exit the function like return, so you cannot use it like return. You are getting this error because you are sending a response more than once.

    I would suggest structuring your logic to build a Response object, then send the response once it is built.

    Example Response Object:

    class Response{
    constructor(status, body){
        this.status = status;
        this.body = body;
    }
}

    Example Usage:

    ...

var response;

if(!result){
    response = new Response(201, {error: "User or password invalid"});
}

if(!response){
    const userForToken = {
        id: users._id,
        name: users.name,
    }

    const token = jwt.sign(userForToken, process.env.SECRET)

    response = new Response(200, {name: users.name, email: users.email, token: token, result: true, id: users._id})
}

res.status(response.status).send(response.body);
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