Node.js/Firebase: can't set headers after they're sent











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We have an express.js/firebase project with an /api/progress POST route that takes a marker as a parameter and increments it if the scanned marker equals the current progress of the user in an array that stores a story order. For that, we have a GET route /api/progress that returns the user progress. We check if the number of the scanned marker equals the storyOrder[userProgress] (minus one because of array indices), user progress is obtained from the api/progress/?user="user" route.



When Number(marker) === storyOrder[response.data.data]-1, we increment the progress in the firebase database by one. However, when the code is run, it sometimes produces the following error:



Error: Can't set headers after they are sent.
at validateHeader (_http_outgoing.js:491:11)
at ServerResponse.setHeader (_http_outgoing.js:498:3)
at ServerResponse.header (/Users/user/Documents/projects/project/node_modules/express/lib/response.js:767:10)
at ServerResponse.send (/Users/user/Documents/projects/project/node_modules/express/lib/response.js:170:12)
at ServerResponse.json (/Users/user/Documents/projects/project/node_modules/express/lib/response.js:267:15)
at userDB.on.data (file:///Users/user/Documents/projects/project/routes/api.mjs:104:15)
at /Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:4465:22
at exceptionGuard (/Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:691:9)
at EventList.raise (/Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:9727:17)
at EventQueue.raiseQueuedEventsMatchingPredicate_ (/Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:9681:41)


This is the code for the /api/progress GET and POST routes:



GET progress:



router.get('/progress', async (req, res, next) => {
let name = req.query.user || null;
console.log('Name: ',name);
let progress;
let dataList;

try {
const getData = async data => {
if (data.val()) {
let tmp = await data.val();
progress = parseInt(tmp[name].progressCounter);
console.log(progress);
// Return progress
res.json({ status: 200, data: progress });
} else {
res.json({ status: 500, err: 'No data! ' });
}
};

const errData = error => {
console.error('Something went wrong.');
console.error(error);
};

dataList = await userDB
.orderByKey()
.equalTo(name)
.on('value', getData, errData);
} catch (err) {
console.log('Error: ', err.message)
res.json({ status: 500, err: 'Error while getting progress' });
}

});


POST progress:



router.post('/progress', async (req, res, next) => {
const user = req.session.user;
const marker = req.body.marker;
if (marker!== undefined) {
const updateProgress = async progress => {
let updateProg = progress.data;
updateProg++;
await userDB.child(user).update({ progressCounter: updateProg });
res.json({ status: 200, marker: updateProg });
};
axios
.get(`http://localhost:5000/api/progress?user=${user}`)
.then(function(response) {
console.log(storyOrder[response.data.data]-1);
if (Number(marker) === storyOrder[response.data.data]-1) {
updateProgress(response.data);
} else {
res.status(304);
res.json({ status: 304 });
}
})
.catch(function(error) {
console.log(error);
});
}else{
res.json({status: 304})
}

});









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    We have an express.js/firebase project with an /api/progress POST route that takes a marker as a parameter and increments it if the scanned marker equals the current progress of the user in an array that stores a story order. For that, we have a GET route /api/progress that returns the user progress. We check if the number of the scanned marker equals the storyOrder[userProgress] (minus one because of array indices), user progress is obtained from the api/progress/?user="user" route.



    When Number(marker) === storyOrder[response.data.data]-1, we increment the progress in the firebase database by one. However, when the code is run, it sometimes produces the following error:



    Error: Can't set headers after they are sent.
    at validateHeader (_http_outgoing.js:491:11)
    at ServerResponse.setHeader (_http_outgoing.js:498:3)
    at ServerResponse.header (/Users/user/Documents/projects/project/node_modules/express/lib/response.js:767:10)
    at ServerResponse.send (/Users/user/Documents/projects/project/node_modules/express/lib/response.js:170:12)
    at ServerResponse.json (/Users/user/Documents/projects/project/node_modules/express/lib/response.js:267:15)
    at userDB.on.data (file:///Users/user/Documents/projects/project/routes/api.mjs:104:15)
    at /Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:4465:22
    at exceptionGuard (/Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:691:9)
    at EventList.raise (/Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:9727:17)
    at EventQueue.raiseQueuedEventsMatchingPredicate_ (/Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:9681:41)


    This is the code for the /api/progress GET and POST routes:



    GET progress:



    router.get('/progress', async (req, res, next) => {
    let name = req.query.user || null;
    console.log('Name: ',name);
    let progress;
    let dataList;

    try {
    const getData = async data => {
    if (data.val()) {
    let tmp = await data.val();
    progress = parseInt(tmp[name].progressCounter);
    console.log(progress);
    // Return progress
    res.json({ status: 200, data: progress });
    } else {
    res.json({ status: 500, err: 'No data! ' });
    }
    };

    const errData = error => {
    console.error('Something went wrong.');
    console.error(error);
    };

    dataList = await userDB
    .orderByKey()
    .equalTo(name)
    .on('value', getData, errData);
    } catch (err) {
    console.log('Error: ', err.message)
    res.json({ status: 500, err: 'Error while getting progress' });
    }

    });


    POST progress:



    router.post('/progress', async (req, res, next) => {
    const user = req.session.user;
    const marker = req.body.marker;
    if (marker!== undefined) {
    const updateProgress = async progress => {
    let updateProg = progress.data;
    updateProg++;
    await userDB.child(user).update({ progressCounter: updateProg });
    res.json({ status: 200, marker: updateProg });
    };
    axios
    .get(`http://localhost:5000/api/progress?user=${user}`)
    .then(function(response) {
    console.log(storyOrder[response.data.data]-1);
    if (Number(marker) === storyOrder[response.data.data]-1) {
    updateProgress(response.data);
    } else {
    res.status(304);
    res.json({ status: 304 });
    }
    })
    .catch(function(error) {
    console.log(error);
    });
    }else{
    res.json({status: 304})
    }

    });









    share|improve this question







    New contributor




    Alexander von Recum is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.






















      up vote
      0
      down vote

      favorite









      up vote
      0
      down vote

      favorite











      We have an express.js/firebase project with an /api/progress POST route that takes a marker as a parameter and increments it if the scanned marker equals the current progress of the user in an array that stores a story order. For that, we have a GET route /api/progress that returns the user progress. We check if the number of the scanned marker equals the storyOrder[userProgress] (minus one because of array indices), user progress is obtained from the api/progress/?user="user" route.



      When Number(marker) === storyOrder[response.data.data]-1, we increment the progress in the firebase database by one. However, when the code is run, it sometimes produces the following error:



      Error: Can't set headers after they are sent.
      at validateHeader (_http_outgoing.js:491:11)
      at ServerResponse.setHeader (_http_outgoing.js:498:3)
      at ServerResponse.header (/Users/user/Documents/projects/project/node_modules/express/lib/response.js:767:10)
      at ServerResponse.send (/Users/user/Documents/projects/project/node_modules/express/lib/response.js:170:12)
      at ServerResponse.json (/Users/user/Documents/projects/project/node_modules/express/lib/response.js:267:15)
      at userDB.on.data (file:///Users/user/Documents/projects/project/routes/api.mjs:104:15)
      at /Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:4465:22
      at exceptionGuard (/Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:691:9)
      at EventList.raise (/Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:9727:17)
      at EventQueue.raiseQueuedEventsMatchingPredicate_ (/Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:9681:41)


      This is the code for the /api/progress GET and POST routes:



      GET progress:



      router.get('/progress', async (req, res, next) => {
      let name = req.query.user || null;
      console.log('Name: ',name);
      let progress;
      let dataList;

      try {
      const getData = async data => {
      if (data.val()) {
      let tmp = await data.val();
      progress = parseInt(tmp[name].progressCounter);
      console.log(progress);
      // Return progress
      res.json({ status: 200, data: progress });
      } else {
      res.json({ status: 500, err: 'No data! ' });
      }
      };

      const errData = error => {
      console.error('Something went wrong.');
      console.error(error);
      };

      dataList = await userDB
      .orderByKey()
      .equalTo(name)
      .on('value', getData, errData);
      } catch (err) {
      console.log('Error: ', err.message)
      res.json({ status: 500, err: 'Error while getting progress' });
      }

      });


      POST progress:



      router.post('/progress', async (req, res, next) => {
      const user = req.session.user;
      const marker = req.body.marker;
      if (marker!== undefined) {
      const updateProgress = async progress => {
      let updateProg = progress.data;
      updateProg++;
      await userDB.child(user).update({ progressCounter: updateProg });
      res.json({ status: 200, marker: updateProg });
      };
      axios
      .get(`http://localhost:5000/api/progress?user=${user}`)
      .then(function(response) {
      console.log(storyOrder[response.data.data]-1);
      if (Number(marker) === storyOrder[response.data.data]-1) {
      updateProgress(response.data);
      } else {
      res.status(304);
      res.json({ status: 304 });
      }
      })
      .catch(function(error) {
      console.log(error);
      });
      }else{
      res.json({status: 304})
      }

      });









      share|improve this question







      New contributor




      Alexander von Recum is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      We have an express.js/firebase project with an /api/progress POST route that takes a marker as a parameter and increments it if the scanned marker equals the current progress of the user in an array that stores a story order. For that, we have a GET route /api/progress that returns the user progress. We check if the number of the scanned marker equals the storyOrder[userProgress] (minus one because of array indices), user progress is obtained from the api/progress/?user="user" route.



      When Number(marker) === storyOrder[response.data.data]-1, we increment the progress in the firebase database by one. However, when the code is run, it sometimes produces the following error:



      Error: Can't set headers after they are sent.
      at validateHeader (_http_outgoing.js:491:11)
      at ServerResponse.setHeader (_http_outgoing.js:498:3)
      at ServerResponse.header (/Users/user/Documents/projects/project/node_modules/express/lib/response.js:767:10)
      at ServerResponse.send (/Users/user/Documents/projects/project/node_modules/express/lib/response.js:170:12)
      at ServerResponse.json (/Users/user/Documents/projects/project/node_modules/express/lib/response.js:267:15)
      at userDB.on.data (file:///Users/user/Documents/projects/project/routes/api.mjs:104:15)
      at /Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:4465:22
      at exceptionGuard (/Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:691:9)
      at EventList.raise (/Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:9727:17)
      at EventQueue.raiseQueuedEventsMatchingPredicate_ (/Users/user/Documents/projects/project/node_modules/@firebase/database/dist/index.node.cjs.js:9681:41)


      This is the code for the /api/progress GET and POST routes:



      GET progress:



      router.get('/progress', async (req, res, next) => {
      let name = req.query.user || null;
      console.log('Name: ',name);
      let progress;
      let dataList;

      try {
      const getData = async data => {
      if (data.val()) {
      let tmp = await data.val();
      progress = parseInt(tmp[name].progressCounter);
      console.log(progress);
      // Return progress
      res.json({ status: 200, data: progress });
      } else {
      res.json({ status: 500, err: 'No data! ' });
      }
      };

      const errData = error => {
      console.error('Something went wrong.');
      console.error(error);
      };

      dataList = await userDB
      .orderByKey()
      .equalTo(name)
      .on('value', getData, errData);
      } catch (err) {
      console.log('Error: ', err.message)
      res.json({ status: 500, err: 'Error while getting progress' });
      }

      });


      POST progress:



      router.post('/progress', async (req, res, next) => {
      const user = req.session.user;
      const marker = req.body.marker;
      if (marker!== undefined) {
      const updateProgress = async progress => {
      let updateProg = progress.data;
      updateProg++;
      await userDB.child(user).update({ progressCounter: updateProg });
      res.json({ status: 200, marker: updateProg });
      };
      axios
      .get(`http://localhost:5000/api/progress?user=${user}`)
      .then(function(response) {
      console.log(storyOrder[response.data.data]-1);
      if (Number(marker) === storyOrder[response.data.data]-1) {
      updateProgress(response.data);
      } else {
      res.status(304);
      res.json({ status: 304 });
      }
      })
      .catch(function(error) {
      console.log(error);
      });
      }else{
      res.json({status: 304})
      }

      });






      node.js firebase express






      share|improve this question







      New contributor




      Alexander von Recum is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      share|improve this question







      New contributor




      Alexander von Recum is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.









      share|improve this question




      share|improve this question






      New contributor




      Alexander von Recum is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.









      asked yesterday









      Alexander von Recum

      31




      31




      New contributor




      Alexander von Recum is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.





      New contributor





      Alexander von Recum is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






      Alexander von Recum is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.
























          1 Answer
          1






          active

          oldest

          votes

















          up vote
          0
          down vote



          accepted










          You are getting that error because, your calling res.send() in the middle of your function and the code continues



          This piece of code is called



          const getData = async data => {
          if (data.val()) {
          let tmp = await data.val();
          progress = parseInt(tmp[name].progressCounter);
          console.log(progress);
          // Return progress
          res.json({ status: 200, data: progress });
          } else {
          res.json({ status: 500, err: 'No data! ' });
          }


          since an error occurs, is called



          res.json({ status: 500, err: 'No data! ' });


          And then this



          dataList = await userDB
          .orderByKey()
          .equalTo(name)
          .on('value', getData, errData);
          } catch (err) {
          console.log('Error: ', err.message)
          res.json({ status: 500, err: 'Error while getting progress' });
          }


          That will call again the first piece of code with a new res.json, but since the response was already sent, you get that error






          share|improve this answer





















          • Thank you very much! This solved the problem.
            – Alexander von Recum
            8 hours ago











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          1 Answer
          1






          active

          oldest

          votes








          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes








          up vote
          0
          down vote



          accepted










          You are getting that error because, your calling res.send() in the middle of your function and the code continues



          This piece of code is called



          const getData = async data => {
          if (data.val()) {
          let tmp = await data.val();
          progress = parseInt(tmp[name].progressCounter);
          console.log(progress);
          // Return progress
          res.json({ status: 200, data: progress });
          } else {
          res.json({ status: 500, err: 'No data! ' });
          }


          since an error occurs, is called



          res.json({ status: 500, err: 'No data! ' });


          And then this



          dataList = await userDB
          .orderByKey()
          .equalTo(name)
          .on('value', getData, errData);
          } catch (err) {
          console.log('Error: ', err.message)
          res.json({ status: 500, err: 'Error while getting progress' });
          }


          That will call again the first piece of code with a new res.json, but since the response was already sent, you get that error






          share|improve this answer





















          • Thank you very much! This solved the problem.
            – Alexander von Recum
            8 hours ago















          up vote
          0
          down vote



          accepted










          You are getting that error because, your calling res.send() in the middle of your function and the code continues



          This piece of code is called



          const getData = async data => {
          if (data.val()) {
          let tmp = await data.val();
          progress = parseInt(tmp[name].progressCounter);
          console.log(progress);
          // Return progress
          res.json({ status: 200, data: progress });
          } else {
          res.json({ status: 500, err: 'No data! ' });
          }


          since an error occurs, is called



          res.json({ status: 500, err: 'No data! ' });


          And then this



          dataList = await userDB
          .orderByKey()
          .equalTo(name)
          .on('value', getData, errData);
          } catch (err) {
          console.log('Error: ', err.message)
          res.json({ status: 500, err: 'Error while getting progress' });
          }


          That will call again the first piece of code with a new res.json, but since the response was already sent, you get that error






          share|improve this answer





















          • Thank you very much! This solved the problem.
            – Alexander von Recum
            8 hours ago













          up vote
          0
          down vote



          accepted







          up vote
          0
          down vote



          accepted






          You are getting that error because, your calling res.send() in the middle of your function and the code continues



          This piece of code is called



          const getData = async data => {
          if (data.val()) {
          let tmp = await data.val();
          progress = parseInt(tmp[name].progressCounter);
          console.log(progress);
          // Return progress
          res.json({ status: 200, data: progress });
          } else {
          res.json({ status: 500, err: 'No data! ' });
          }


          since an error occurs, is called



          res.json({ status: 500, err: 'No data! ' });


          And then this



          dataList = await userDB
          .orderByKey()
          .equalTo(name)
          .on('value', getData, errData);
          } catch (err) {
          console.log('Error: ', err.message)
          res.json({ status: 500, err: 'Error while getting progress' });
          }


          That will call again the first piece of code with a new res.json, but since the response was already sent, you get that error






          share|improve this answer












          You are getting that error because, your calling res.send() in the middle of your function and the code continues



          This piece of code is called



          const getData = async data => {
          if (data.val()) {
          let tmp = await data.val();
          progress = parseInt(tmp[name].progressCounter);
          console.log(progress);
          // Return progress
          res.json({ status: 200, data: progress });
          } else {
          res.json({ status: 500, err: 'No data! ' });
          }


          since an error occurs, is called



          res.json({ status: 500, err: 'No data! ' });


          And then this



          dataList = await userDB
          .orderByKey()
          .equalTo(name)
          .on('value', getData, errData);
          } catch (err) {
          console.log('Error: ', err.message)
          res.json({ status: 500, err: 'Error while getting progress' });
          }


          That will call again the first piece of code with a new res.json, but since the response was already sent, you get that error







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered yesterday









          Pedro Silva

          35910




          35910












          • Thank you very much! This solved the problem.
            – Alexander von Recum
            8 hours ago


















          • Thank you very much! This solved the problem.
            – Alexander von Recum
            8 hours ago
















          Thank you very much! This solved the problem.
          – Alexander von Recum
          8 hours ago




          Thank you very much! This solved the problem.
          – Alexander von Recum
          8 hours ago










          Alexander von Recum is a new contributor. Be nice, and check out our Code of Conduct.










           

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          Alexander von Recum is a new contributor. Be nice, and check out our Code of Conduct.













          Alexander von Recum is a new contributor. Be nice, and check out our Code of Conduct.












          Alexander von Recum is a new contributor. Be nice, and check out our Code of Conduct.















           


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