Model.Store.find().where({ date: { $lte: dateref } }).exec((err, stores) => {
    stores.forEach(element => {
      Model.Store.deleteOne({ _id: element._id }, (err, store) => {
        if (err) {
          return console.log(err);
        }
      });
      console.log('routine de suppression de la collection "Store" périmée dans la bdd OK : ' + element.creator);
    });
    Model.Store.find({}).then((elements) => {
      var count;
      var reference;
      elements.forEach(element => {
        count = element.recipients.length;
        console.log('number of recipients : ' + count);
        element.documents.forEach(doc => {
          reference = doc.downloadConfirmed.length;
          console.log('reference = '+ reference+', documents._id = '+doc._id)
          if (count === reference) {
            Model.Store.findOneAndUpdate({ "documents.$._id": doc._id },
              { $pull: { documents: { _id: doc._id } } }  ) // doesn't work, must find the correct command!!
              .then((result) => {
                console.log(result);
            })
          }
        })
      })
    }).catch((err) => {
      if (err) {
        console.log(err);
      }
    });
  });