CODEWITHSUNDEEP
node.jsexpress
user19485562
user19485562

Reputation:

Using next() and res.send .Cannot set headers after they are sent to the client. Error [ERR_HTTP_HEADERS_SENT]:

I am new to node js and express and learning the basicsss,, In other code errors i saw, i used to debug by seeing the throws part but itsnt here..

EDIT: I am new to the concept of middleware & next()and that has created the error as seen in upvoted answer.

Code :

const express = require('express')
const app = express()

app.use('/add-product',(req,res,next)=>{
    console.log("This is add-product page")
    res.send("<form action='/product' method ='POST'><input type='text' name ='title'><button type ='submit'>Submit</button></form> ")
    next()
})
app.use('/product',(req,res,next)=>{
    console.log('this is product-page')
    res.redirect('/')
})
app.use('/', (req,res,next)=>{
    res.send('Welcome to NodeJS')
})
app.listen(3000)

Error :

[nodemon] starting `node app.js`
This is add-product page
Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at new NodeError (node:internal/errors:387:5)
    at ServerResponse.setHeader (node:_http_outgoing:603:11)
    at ServerResponse.header (C:\Users\A\Desktop\vs code\the complete tutorial\node_modules\express\lib\response.js:794:10)
    at ServerResponse.contentType (C:\Users\A\Desktop\vs code\the complete tutorial\node_modules\express\lib\response.js:624:15)
    at ServerResponse.send (C:\Users\A\Desktop\vs code\the complete tutorial\node_modules\express\lib\response.js:149:14)
    at C:\Users\A\Desktop\vs code\the complete tutorial\app.js:14:9
    at Layer.handle [as handle_request] (C:\Users\A\Desktop\vs code\the complete tutorial\node_modules\express\lib\router\layer.js:95:5)
    at trim_prefix (C:\Users\A\Desktop\vs code\the complete tutorial\node_modules\express\lib\router\index.js:328:13)
    at C:\Users\A\Desktop\vs code\the complete tutorial\node_modules\express\lib\router\index.js:286:9
    at Function.process_params (C:\Users\A\Desktop\vs code\the complete tutorial\node_modules\express\lib\router\index.js:346:12)

Upvotes: 0

Views: 1082

Answers (3)

Shrey Banugaria
Shrey Banugaria

Reputation: 165

When you are finished with processing your request, fetching data and want to send the final response, use return before the res.send()

The above error you are facing is because of the next() function you are calling in the '/add-product'. It will check for the next function to be called.

next() function is used when you want another function to run for the same route after calling a function.

Try this:

app.use('/add-product', (req, res, next) => {
  console.log("This is add-product page")
  return res.send("<form action='/product' method ='POST'><input type='text' name ='title'><button type ='submit'>Submit</button></form>");
});

Upvotes: 1

Nguyen Cong Minh
Nguyen Cong Minh

Reputation: 34

app.use('/add-product',(req,res,next)=>{
    console.log("This is add-product page")
    res.send("<form action='/product' method ='POST'><input type='text' name ='title'><button type ='submit'>Submit</button></form> ")
    next()
})

After you res.send(...) you can't next here. Use next() func when you want to create a middleware with condition.

Upvotes: 1

Drashti Kheni
Drashti Kheni

Reputation: 1140

You should always use return while sending response to client.

const express = require('express')
const app = express()

app.use('/add-product',(req,res,next)=>{
    console.log("This is add-product page")
    return res.send("<form action='/product' method ='POST'><input type='text' name ='title'><button type ='submit'>Submit</button></form> ")
    
})
app.use('/product',(req,res,next)=>{
    console.log('this is product-page')
    return res.redirect('/')
})
app.use('/', (req,res,next)=>{
    return res.send('Welcome to NodeJS')
})
app.listen(3000)

Upvotes: 0

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