Node + Mongoose, wait for result before saving

Question

I am actually trying to save a new record in my mongodb databse.

   company.save(function(err, company){
        if (err)
            //fail;

    //success
    })

But, before this action, i'd like to add tags to my company

My company schema

var companySchema = new mongoose.Schema({
    name: String,
    accro: String,
    npa: String,
    city: String,
    country: String,
    isverified : Boolean,
    tags: [{
        type: mongoose.Schema.Types.ObjectId,
        ref: 'Tag'  //  réf. tagSchema
    }
    ]
})

as you can see, tags is a ref so i'm checking if the tag already exists or not:

for (var i = 0; i < req.body.tags.length; i++) {
        var currentTag = req.body.tags[i];

        Tag.findOne({'label': currentTag }, function(err,t){
            var tag_id = "";

            if(err) res.send(err);

            // if exist
            if (t) {
                console.log("#" + i + " currentTag existe");
                t.use++;
                t.save();
                tag_id = t._id;

            } else {

                console.log("#" + i + " currentTag not existe");
                var tag = new Tag();
                tag.label = currentTag;
                tag.save();
                tag_id = tag._id;
            }

            company.tags.push(tag_id);

        });
    }

but as the mongoose findOne function has a callback, the loop just keeps "looping" and when the company.save() is fired, no tags has been added to the company..

Need some help to get it asynchronous :) Thanks

Answer 1

You need not to find tags one by one. use $in operator like below:

Tag.find({'label': {$in: req.body.tags}},function(err,oldTags){


            if(err) res.send(err);
var tag_id = '';
            for(var i = 0; i < req.body.tags.length; i++){
              for(var j = 0; j < oldTags.length; j++){

              if(req.body.tags[i] == oldTags[j].label){
               oldTags[j].use++;
               oldTags[j].save(function(err, tag) {
                                company.tags.push(tag._id);


});
              } else {
              console.log("#" + i + " currentTag not existe");
              var tag = new Tag();
              tag.label = req.body.tags[i];
              tag.save(function(err, newTag) {
                                company.tags.push(newTag._id);


});
              }

            }
            }
// HERE SAVE YOUR COMPANY OBJECT
        });

UPDATE

Tag.find({
    'label': {
        $in: req.body.tags
    }
}, function(err, oldTags) {

    if (err) res.send(err);
    var tags_id = [];
    var db_labels = [];
    var db_ids = [];
    var new_tags = [];

    for (var i = 0; i < oldTags.length; i++) {
        db_labels.push(oldTags[i].label);
        db_ids.push(oldTags[i]._id);
    }

    for (var i = 0; i < req.body.tags.length; i++) {
        var label = req.body.tags[i].trim().toUpperCase();
        var tag_id = "";
        if (db_labels.indexOf(label) == -1) {

            //tag not found
            //var tag = new Tag();
            //tag.label = label;
            new_tags.push({
                    label: label
                })
                // tag.save(function(err, newTag) {
                //     tags_id.push(newTag._id);
                // });

        } else {

            //tag found
            tags_id.push(db_ids[db_labels.indexOf(label)]);

        }
    }

    Tag.collection.insert(new_tags, function(err, data) {
        tags_id = tags_id.concat(data.insertedIds);
        company.tags = tags_id;
        company.save(function(err, company) {
            if (err)
                res.send(err);

            res.json(company);
        })
    });
});

Answer 2

Following @Sachin answer: got this:

    Tag.find({'label': {$in: req.body.tags}},function(err,oldTags){

      if(err) res.send(err);
                var tags_id = [];
                var db_labels = [];
                var db_ids = [];

                for (var i = 0; i < oldTags.length; i++) {
                    db_labels.push( oldTags[i].label );
                    db_ids.push( oldTags[i]._id );
                }

                for (var i = 0; i < req.body.tags.length; i++) {
                    var label = req.body.tags[i].trim().toUpperCase();
                    var tag_id = "";
                    if ( db_labels.indexOf(label) == -1) {

                        //tag not found
                        var tag = new Tag();
                        tag.label = label;
                        tag_id = tag._id;
                        tag.save();

                    } else {

                        //tag found
                        tag_id = db_ids[db_labels.indexOf(label)];

                    }
                    tags_id.push( tag_id )
                }

                company.tags = tags_id;
                company.save(function(err, company){
                    if (err)
                        res.send(err);

                    res.json(company);
                })
    });

Answer 3

Pattern you are looking for is promise.all

var q = require('q');
var arr = [];
for (var i = 0; i < req.body.tags.length; i++) {
    //check if tag exist and if not create 
    var promise = tag.save();
    arr.add(promise) 
}


q.all(arr).then(function(newArr) { //check what comes in newArr and set it in company tags
   company.tags.push(newArr);
   //save company
});