json - Can't set headers after they are sent. Nodejs/express with axios -

i have seen error , more wanting know how work around it. need able output data json object. there anyway work around this.

i copying , pasting tutorial , not sure why im getting here except deep request calls maybe?

here error:

error: can't set headers after sent. [0]     @ serverresponse.outgoingmessage.setheader (_http_outgoing.js:344:11) [0]     @ serverresponse.header (c:\users\amazo\thrifa\moovr\node_modules\keystone\node_modules\express\lib\response.js:730:10) [0]     @ serverresponse.send (c:\users\amazo\thrifa\moovr\node_modules\keystone\node_modules\express\lib\response.js:170:12) [0]     @ serverresponse.json (c:\users\amazo\thrifa\moovr\node_modules\keystone\node_modules\express\lib\response.js:256:15) [0]     @ c:/users/amazo/thrifa/moovr/src/server/api/routes/offers.js:28:21 [0]     @ promise.<anonymous> (c:/users/amazo/thrifa/moovr/src/server/api/controllers/store/offercontroller.js:25:7) [0]     @ promise.<anonymous> (c:\users\amazo\thrifa\moovr\node_modules\keystone\node_modules\mongoose\node_modules\mpromise\lib\promise.js:177:8) [0]     @ emitone (events.js:77:13) [0]     @ promise.emit (events.js:169:7) [0]     @ promise.emit (c:\users\amazo\thrifa\moovr\node_modules\keystone\node_modules\mongoose\node_modules\mpromise\lib\promise.js:84:38) [0]     @ promise.fulfill (c:\users\amazo\thrifa\moovr\node_modules\keystone\node_modules\mongoose\node_modules\mpromise\lib\promise.js:97:20) [0]     @ c:\users\amazo\thrifa\moovr\node_modules\keystone\node_modules\mongoose\lib\query.js:1406:13 [0]     @ model.document.init (c:\users\amazo\thrifa\moovr\node_modules\keystone\node_modules\mongoose\lib\document.js:254:11) [0]     @ completeone (c:\users\amazo\thrifa\moovr\node_modules\keystone\node_modules\mongoose\lib\query.js:1404:10) [0]     @ immediate.cb (c:\users\amazo\thrifa\moovr\node_modules\keystone\node_modules\mongoose\lib\query.js:1158:11) [0]     @ immediate._onimmediate (c:\users\amazo\thrifa\moovr\node_modules\keystone\node_modules\mongoose\node_modules\mquery\lib\utils.js:137:16) [0]     @ processimmediate [as _immediatecallback] (timers.js:383:17) 

here code:

import offercontroller '../controllers/store/offercontroller'; import requestmanager '../utils/requestmanager'; import axios 'axios';  const offerroutes = (app) => {   app.get('/api/offers', (req, res, next) => {     axios       .get(         'https://d2fzm6xoa70bg8.cloudfront.net/login?auth=e4031de36f45af2172fa8d0f054efcdd8d4dfd62',       )       .then((response) => {         axios           .get('https://d2fzm6xoa70bg8.cloudfront.net/offerfilter?', {             headers: { token: response.data.token },           })           .then((response) => {             const { data } = response;              data.map((item, i) => {               offercontroller.findone({ offer: item.offer }, (err, result) => {                 if (err) {                   res.json({                     message: err,                   });                    return;                 }                 res.json({                   message: 'offer exist',                   result,                 });               });                const params = {                 offer: item.offer,                 cert: item.cert,                 txid: item.txid,                 expires_in: item.expires_in,                 expires_on: item.expires_on,                 expired: item.expired,                 height: item.height,                 time: item.time,                 category: item.category,                 title: item.title,                 quantity: item.quantity,                 currency: item.currency,                 sysprice: item.sysprice,                 price: item.price,                 ismine: item.ismine,                 commission: item.commission,                 offerlink: item.offerlink,                 offerlink_guid: item.offerlink_guid,                 offerlink_seller: item.offerlink_seller,                 private: item.private,                 safesearch: item.safesearch,                 safetylevel: item.safetylevel,                 paymentoptions: item.paymentoptions,                 paymentoptions_display: item.paymentoptions_display,                 alias_peg: item.alias_peg,                 description: item.description,                 alias: item.description,                 address: item.address,                 alias_rating: item.alias_rating,                 alias_rating_count: item.alias_rating_count,                 alias_rating_display: item.alias_rating_display,                 geolocation: item.geolocation,                 offers_sold: item.offers_sold,               };               offercontroller.create(params, (err, results) => {                 if (err) {                   console.log(err);                    return;                 }                  res.write(results);               });             });           })           .catch((err) => {             console.log('err 2nd request', err);             res.json({               confirmation: 'fail after 2nd request',               message: err,             });           });       })       .catch((err) => {         console.log('err 1st request');         res.json({           confirmation: 'fail before 2nd request',           message: err,         });       });   }); }; export default offerroutes; 

you have res.json(...) inside call map means make multiple calls res.json resulting in setting content-type header multiple times same res instance.