Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client - Ayuda no se porque sucede eso

Question

I am new to this topic of Rest Apis, and I was creating a simple one where I receive a json with movie data and give a small response. As I am new I want to start with what would be the logic and it is an array that is saving data.

But when I send data through PostMan, it saves everything well and does its job, but I get this error on the console.

someone who can guide me please

MY CODE

router.post('/', (req, res) => {
    const {titulo, director, year, rating} = req.body;
    if (titulo && director && year && rating) {
        const id = movies.length + 1;
        const newMovie = {...req.body, id};
        movies.push(newMovie);
        res.json(movies);
    } else {
        res.status(500).json({error: 'Ha Ocurrido un error'});
    }
    res.send('recibido');
});

module.exports = router;

CMD ERROR

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at new NodeError (node:internal/errors:371:5)
    at ServerResponse.setHeader (node:_http_outgoing:576:11)
    at ServerResponse.header (C:\Users\ManuelLeigh\Desktop\restapi\node_modules\express\lib\response.js:776:10)
    at ServerResponse.send (C:\Users\ManuelLeigh\Desktop\restapi\node_modules\express\lib\response.js:170:12)
    at C:\Users\ManuelLeigh\Desktop\restapi\src\routes\movies.js:20:9
    at Layer.handle [as handle_request] (C:\Users\ManuelLeigh\Desktop\restapi\node_modules\express\lib\router\layer.js:95:5)
    at next (C:\Users\ManuelLeigh\Desktop\restapi\node_modules\express\lib\router\route.js:137:13)
    at Route.dispatch (C:\Users\ManuelLeigh\Desktop\restapi\node_modules\express\lib\router\route.js:112:3)
    at Layer.handle [as handle_request] (C:\Users\ManuelLeigh\Desktop\restapi\node_modules\express\lib\router\layer.js:95:5)
    at C:\Users\ManuelLeigh\Desktop\restapi\node_modules\express\lib\router\index.js:281:22

Postman Header:

Content-Type: application/json

score 8 · Answer 1 · answered Jan 30 '22 at 13:21

Your code is trying to send response after it is sent. Check for following lines, in if and else,, you are already sending response to server and after this is processed, on last line, you are sending some text.

   if (titulo && director && year && rating) {
        res.json(movies);
    } else {
        res.status(500).json({error: 'Ha Ocurrido un error'});
    }
    res.send('recibido');

Update your code as below,

router.post('/', (req, res) => {
    const {titulo, director, year, rating} = req.body;
    if (titulo && director && year && rating) {
        const id = movies.length + 1;
        const newMovie = {...req.body, id};
        movies.push(newMovie);
        res.json(movies);
    } else {
        res.status(500).json({error: 'Ha Ocurrido un error'});
    }
   // res.send('recibido');
});

module.exports = router;

Thank you very much and excuse my ignorance of these topics – Manuel Leigh Jan 30 '22 at 19:56 — Manuel Leigh, Jan 30 '22 at 19:56

score 3 · Accepted Answer · answered Aug 10 '22 at 20:46

after if-else block, you again try to send response.By putting return after sending response in each block, you can fix your problem or other simple way, just comment res.send("recibido"). simple way is to just comment res.send("recibido")

you can write your code this way:

router.post('/', (req, res) => {
const {titulo, director, year, rating} = req.body;
if (titulo && director && year && rating) {
    const id = movies.length + 1;
    const newMovie = {...req.body, id};
    movies.push(newMovie);
    res.json(movies);      
} else {
    res.status(500).json({error: 'Ha Ocurrido un error'});        
}
   // res.send('recibido');
});

module.exports = router;

score 2 · Answer 3 · answered Sep 06 '22 at 13:57

2

Use return statement for res.json, res.status and res.send provided the if else logic is what you want.

I was encountering the above error in my code only to realise wherever I had a logic statement, for some conditions the code kept on running and needed to return the outcome e.g return res.status(400).send("Error Message)

answered Sep 06 '22 at 13:57

Chief

854
12
27

Yes this worked for me too! Could you please format your answer into a code with an example, it would be better to get an idea at first glimpse. I was also trying to put middleware functions and validation checks with lots of if & else statement, and wasn't returning. – Clinto_92_Abraham May 17 '23 at 06:50

score 0 · Answer 4 · edited Nov 15 '22 at 16:22

0

I found the answer to my error by putting a return, but I don't know how correct this solution is

const isAdmin = async (req, res, next) => {
  if (req.isAuthenticated() && req.user.role === "admin") {
    return next()
  } else {
    req.flash("danger", "not allowed")
    res.redirect("/")
  }
  return next()
}

edited Nov 15 '22 at 16:22

Tyler2P

2,324
26
22
31

answered Nov 11 '22 at 16:12

Komil Maxmudov

1
1

score 0 · Answer 5 · answered Aug 05 '23 at 12:15

For me I used async/await for request and response handler to getover the error. it's something like this:

router.post("/", async (req,res)=>{
   await myFunc(val1,val2).then(()=>{
    res.send("success")
   )
   .catch((err)=>{
    res.send(err)
   )
})

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client - Ayuda no se porque sucede eso

5 Answers5

Linked