Node JS mongoose Query is not producing result

Question

Been stuck on this problem for hours. The below code:

router.route("/contact")
    .get(function(req,res){
        var response = {};
        Contact.find({},function(err,data){
            if(err) {
                response = {"error" : "Error fetching data"};
            } else {
                response = {"message" : data};
            }
            res.json(response);
        });
    })

Above query produces result with all the contacts in the database but

router.route("/contact/department/:dept")
    .get(function(req,res){
        var response = {};
        var arrDept = req.params.dept.split(",");
        if(arrDept.length == 0){
            response = {"error": " Please enter Department keywords"};
        }
        else{
            response = {};
            arrDept.forEach(function(currentValue){
                Video.find({dept: '/'+currentValue+'/i'}, function(err, data){
                    if(err){
                        response[currentValue] = "No data found";
                    }else{
                        response[currentValue] = data;
                    }
                });
            });
        }
        res.json(response);
    });

this code does not produce any output.

The code is entering the forEach loop in the else block but the query is not generating any result even if I modify the query to a basic one like

Video.find({},function(err, data){
                    if(err){
                        response[currentValue] = "No data found";
                    }else{
                        response[currentValue] = data;
                    }
                });

The response JSON is still returned blank.

PS: Problem has been simplified as is only an example of actual problem i am facing in the code. update after answer found.

Karthik Sharma · Accepted Answer · 2016-05-18 09:33:41Z

2

res.json(response)

was written outside the query that is why a blank json was getting returned. The above scenario can be solved using promise as follows:

var promise = Contact.find({ dept: { $in: arrayDept }}).exec(); 
promise.then(function(resultJson) { res.json(resultJson); });

This can be used to execute all the queries in the array and return the complete json.

answered May 18, 2016 at 9:33

Karthik Sharma

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Comments

DAXaholic · Accepted Answer · 2016-05-17 15:43:46Z

1

Your res.json(response); in the non-working example is outside the callback of your MongoDB query, that is you are writing the response before the query's callback was actually executed and therefore your result is empty.

answered May 17, 2016 at 15:43

DAXaholic

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3 Comments

Karthik Sharma Over a year ago

thanks DAXaholic .... but how do i append data from each iteration of the loop to the response json object ?

DAXaholic Over a year ago

To do it without any further helper library you could e.g. maintain an array outside the callback with the results and add to it in the callback and as soon as the size of that array is equal to your 'arrDept' you know you have got all results. But to be honest, it is much easier and straightforward to use something like async.js. See github.com/caolan/async#map for a quick example of what I mean.

Karthik Sharma Over a year ago

thnx... i finally solved it with promise. var promise = Contact.find({ dept: { $in: arrayDept }}).exec(); promise.then(function(resultJson) { res.json(resultJson); });

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