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When I send a GET request : Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client

when I tried to send a get request to the url of my function (on a firebase project ex: http://project_url.com/api/post/id), this error shows
(node:1061) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
> at ServerResponse.setHeader (_http_outgoing.js:518:11)
> at ServerResponse.header (/Users/salvatorebramante/beta/functions/node_modules/express/lib/response.js:771:10)
> at ServerResponse.send (/Users/salvatorebramante/beta/functions/node_modules/express/lib/response.js:170:12)
> at ServerResponse.json (/Users/salvatorebramante/beta/functions/node_modules/express/lib/response.js:267:15)
> at /Users/salvatorebramante/beta/functions/handlers/posts.js:70:25
> at processTicksAndRejections (internal/process/task_queues.js:97:5)
> (node:1061) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 2)
The function returns a json with the infos about a document stored in firebase cloud storage
exports.getPost = (req,res) => {
let postData;
db.doc(`/posts/${req.params.postId}`).get()
.then(doc =>{
if(!doc.exists){
return res.status(404).json({error : 'Post not found'})
}
postData = doc.data();
postData.postId = doc.id;
return db.collection('comments').orderBy('createdAt', 'desc').where('postId','==',req.params.postId).get();
})
.then(data =>{
postId.comments = [];
data.forEach(doc => {
postData.comments.push(doc.data());
})
return res.json(postData);
})
.catch(err =>{
res.status(500).json({ error: err.code });
console.error(err);
});
};
While the error occurred, the get request response is 404, but I've checked that the document id is correct. How can I resolve it?

Why does the function continue running after a return statement?

I am running the following code trying to delete a "scream" that does not exist:
// Delete a scream
exports.deleteScream = (req, res) => {
const document = db.doc(`/screams/${req.params.screamId}`);
document.get()
.then(doc => {
if(!doc.exists){
console.log("1")
return res.status(404).json({ error: 'Scream not found'});
console.log("2")
}
if(doc.data.userHandle !== req.user.handle){
return res.status(403).json({ error: 'Unathorized'});
} else {
return document.delete();
}
})
.then(() => {
console.log("3")
return res.json({ message: 'Scream deleted successfully'});
console.log("4")
})
.catch(err => {
console.error(err);
console.log("5")
return res.status(500).json({ error: err.code });
});
};
The console log shows the follwing:
> 1
> 3
> Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
> at ServerResponse.setHeader (_http_outgoing.js:516:11)
> at ServerResponse.header (/Users/sm/projects/socialape/functions/node_modules/express/lib/response.js:771:10)
> at ServerResponse.send (/Users/sm/projects/socialape/functions/node_modules/express/lib/response.js:170:12)
> at ServerResponse.json (/Users/sm/projects/socialape/functions/node_modules/express/lib/response.js:267:15)
> at /Users/sm/projects/socialape/functions/handlers/screams.js:227:18
> at processTicksAndRejections (internal/process/task_queues.js:93:5) {
> code: 'ERR_HTTP_HEADERS_SENT'
> }
> 5
> (node:4032) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
> at ServerResponse.setHeader (_http_outgoing.js:516:11)
> at ServerResponse.header (/Users/sm/projects/socialape/functions/node_modules/express/lib/response.js:771:10)
> at ServerResponse.send (/Users/sm/projects/socialape/functions/node_modules/express/lib/response.js:170:12)
> at ServerResponse.json (/Users/sm/projects/socialape/functions/node_modules/express/lib/response.js:267:15)
> at /Users/sm/projects/socialape/functions/handlers/screams.js:233:30
> at processTicksAndRejections (internal/process/task_queues.js:93:5)
> (node:4032) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
> (node:4032) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
I would expect the function to stop executing at the 404 response, but it appears like both then blocks are executed in addition the the catch block. Why is this the case?

If you return inside a then function, you are returning only that anonymous function. It is not return from parent. You should throw an exception and return in catch.
const document = db.doc(`/screams/${req.params.screamId}`);
document
.get()
.then(doc => {
if (!doc.exists) throw new Error(404);
return doc;
})
.then(doc => {
if (doc.data.userHandle !== req.user.handle) {
throw new Error(403);
} else {
document.delete();
}
return doc;
})
.then(() => {
res.json({ message: "Scream deleted successfully" });
})
.catch(error => {
switch (error.message) {
case 403:
res.status(error.message).send({ error: "Unathorized" });
break;
case 404:
res.status(error.message).send({ error: "Scream not found" });
break;
default:
res.status(error.message).send({ error: error.message });
break;
}
});

Express "UnhandledPromiseRejectionWarning: RangeError" in login middleware

I'm doing a RESTful API for a vuejs frontend with authentication and data saving by account.
I get this error when trying to log a user in.
Basically my frontend will send a request with a body containing a username and password.
Here's the log in middleware in express :
exports.post_LogIn = (req, res, next) => {
User.findOne({ username: req.body.username })
.then(foundUser => {
if (!foundUser) {
console.log("no user");
const error = new Error("No user with that username");
error.statusCode = 400;
error.tosend = "No user with that username";
throw error;
} else {
return bcrypt.compare(req.body.password, foundUser.password);
}
})
.then(isEqual => {
if (!isEqual) {
console.log("wrong password");
const error = new Error("Passwords don't match");
error.statusCode = 400;
error.tosend = "Passwords don't match";
throw error;
}
console.log("logged in");
const token = jwt.sign(
{
username: foundUser.username
},
"secretpassword",
{ expiresIn: "24h" }
);
console.log(token);
res.status(200).json({ username: foundUser.username });
})
.catch(err => {
res.status(err.statusCode).json({ message: err.tosend });
});
};
So basically when there's a problem with the credentials (either wrong username or password) I wanna send a response to the front end with a message saying what was wrong, and let the front end deal with it.
This works just fine and as expected.
However when I send valid credentials, my console.log statement goes through, but the token and response part gives me this error
(node:14515) UnhandledPromiseRejectionWarning: RangeError
[ERR_HTTP_INVALID_STATUS_CODE]: Invalid status code: undefined
at ServerResponse.writeHead (_http_server.js:242:11)
at ServerResponse._implicitHeader (_http_server.js:233:8)
at write_ (_http_outgoing.js:579:9)
at ServerResponse.end (_http_outgoing.js:689:5)
at ServerResponse.send (/home/martin/dev/projets/trader-backend/node_modules/express/lib/response.js:221:10)
at ServerResponse.json (/home/martin/dev/projets/trader-backend/node_modules/express/lib/response.js:267:15)
at /home/martin/dev/projets/trader-backend/controllers/UserController.js:97:34
(node:14515) UnhandledPromiseRejectionWarning: Unhandled promise
rejection. This error originated either by throwing inside of an async
function without a catch block, or by rejecting a promise which was
not handled with .catch(). (rejection id: 1) (node:14515) [DEP0018]
DeprecationWarning: Unhandled promise rejections are deprecated. In
the future, promise rejections that are not handled will terminate the
Node.js process with a non-zero exit code.
I tried commenting out the token part, or commenting the response and console logging the token, and I still get the same error.
However if I comment out the token and use res.send instead of res.json it seems to be working fine and my front end gets the response.
Any idea what might be causing this ? I'm kind of lost here

DeprecationWarnings in nodejs application

my user.js
const express=require('express')
const router=express.Router()
const gravatar=require('gravatar')
const bcrypt=require('bcryptjs')
const {check,validationResult} =require('express-validator/check')
const User=require('../../models/User')
//#route POST api/users
//#desc Register user
//#access public
router.post('/',[
check('name','Name is required').not().isEmpty(),
check('email','please include a valid email').isEmail(),
check('password','please enter password with more than 6 characters').isLength({min:6})
],async(req,res)=>{
const errors=validationResult(req);
if(!errors.isEmpty()){
return res.status(400).json({errors:errors.array()})
}
const {name,email,password}=req.body;
try{
//see if the user exists
let user = await User.findOne({ email: email })
//if record exists in DB
if (user) {
return res.status(400).json({ errors: [{ msg: "user already exists" }] });
}
//get users gravatar
const avatar=gravatar.url(email,{
s:'200', //size
r:'pg', //rating of image
d:'mm' //gives a default image
})
user=new User({
name,
email,
avatar,
password
})
//encrpyt password
const salt=await bcrypt.genSalt(10) // 10-no of rounds.more the better
user.password=await bcrypt.hash(password,salt); //coverts to hash pass
await user.save();
//return jsonwebtoken
res.send('User registered')
}catch(e){
console.log(e.message)
res.status(500).send('server error')
}
res.send('User route')
})
module.exports=router;
the app is working fine but in the terminal i get
(node:1022) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
at ServerResponse.setHeader (_http_outgoing.js:464:11)
at ServerResponse.header (/Users/udayshetty/Desktop/MERN app/node_modules/express/lib/response.js:771:10)
at ServerResponse.send (/Users/udayshetty/Desktop/MERN app/node_modules/express/lib/response.js:170:12)
at /Users/udayshetty/Desktop/MERN app/routes/api/users.js:60:9
at processTicksAndRejections (internal/process/task_queues.js:85:5)
(node:1022) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:1022) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

This error occurs when your app is responding to the client over HTTP - and you try to send the response / response headers twice. Once the response is sent, the connection will be closed. You can only send them once for a given http request. You can keep a connection open and send more data , but you cannot send the response headers again.
Please try to remove res.send('User route').
You are sending a response twice.

nodejs crash only when I send multiple request

node js thunder when I send multiple requests to the server at the same time, but not when I send one by one. And nodejs says.
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
(node:4) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 6)
That error in common when you send two responses to the client but in my code only sent one
This is my code
const User = require('../../../modelos/users');
async function getAllValuationsByUserName(req, res, next) {
let isOwner = false;
const userId = req.params.id;
const pagination = {
skip: Number(req.query.skip),
limit: Number(req.query.limit)
}
if (userId === res.locals.userid) {
isOwner = true;
}
try {
const user = await User.findOne(
{ userName: new RegExp('^' + userId + '$', "i") },
{
'userPhoto.valuations': {
$slice: [pagination.skip, pagination.limit]
}
})
const valuations = user.userPhoto.valuations
const total = user.userPhoto.valuations.length
return res.status(200).send({
erro: false,
isOwner,
valuations,
total
})
} catch (err) {
console.log(err)
return res.status(400).send({
error: true,
inf: err
});
}
}
module.exports = getAllValuationsByUserName