Adding an array as element to an array in javascript

Question

Node, express, mongoose.

I am trying to add an Array as an element to an Array from a callback.

app.get('/view', function(req, res){
    var csvRows = [];
    Invitation.find({}, function(err, invitations){
       if(err){
           console.log('error');
       } else {

           invitations.forEach(function(invitation){
               Guest.find({_id: invitation.guests}, function(err, guest){
                   if(err){

                   } else {
                       var rsvpURL = 'url'+invitation._id;

                        var csvRow = [guest[0].firstName, 
                                    guest[0].addr1, 
                                   ...,
                                    rsvpURL];
                        csvRows.push(csvRow);

                   }
               });
           });
           console.log(csvRows);
           res.send(csvRows);
       }

    });
});

The array gets nothing added to it. Any thoughts will be greatly appreciated.

You're trying to return the array before the asynchronous operations have finished. — Pointy
– Pointy, Commented Apr 23, 2018 at 23:38

CertainPerformance · Accepted Answer · 2018-04-23 23:44:23Z

1

Await the Promise.all over each found guest, returning a promise that resolves to the desired row:

app.get('/view', function(req, res){
  Invitation.find({}, async function(err, invitations){
    if(err){
      console.log('error');
      return;
    }
    const csvRows = await Promise.all(invitations.map(function(invitation){
      return new Promise((resolve, reject) => {
        Guest.find({_id: invitation.guests}, function(err, guest){
          if(err){
            console.log('error');
            reject();
          }
          const rsvpURL = 'url'+invitation._id;
          const csvRow = [guest[0].firstName, guest[0].addr1, rsvpURL];
          resolve(csvRow);
        });
      });
    }));

    console.log(csvRows);
    res.send(csvRows);
  });
});

answered Apr 23, 2018 at 23:44

CertainPerformance

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1 Comment

N. Desai Over a year ago

Thank you! FYI to anyone else reading this make sure you are using node 7+ to implement this solution.

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