Updating problems with submit request, jQuery, MongoDB and Mongoose

Question

I am trying to create an application using MongoDB, Mongoose, JQuery and Node.js. Whenever I try to add to an array in my schema, sometimes it will add this element several times.

Scheme

This is my scheme, I'm trying to add my upvote and downvote arrays that track users who voted by their id.

    var SuggestionSchema = new mongoose.Schema ({
      title: String,
      content: String,
      link: String,
      upvote: [{
        user_id: {
        type: Schema.ObjectId,
        ref: 'User'
        }
      }],
      downvote: [{
        user_id: {
        type: Schema.ObjectId,
        ref: 'User'
        }
      }],
      user_id: {
        type: Schema.ObjectId,
        ref: 'User'
      },
      category_id: {
        type: Schema.ObjectId,
        ref: 'Category'
      },
    });

Route and request

Here is my route and request

    router.put('/:suggestion_id/downvote', function(req, res, next) {
      Suggestion.findByIdAndUpdate(
      req.params.suggestion_id,
      {$push: {"downvote": req.body}},
      function(err, suggestion) {
        res.json(suggestion);
      })
    });

Ajax Call JQuery

PUT, .

$('#downvote').click(function(){

    var user = {
        user_id: current_user._id
    }

    $.ajax({
        url: current_url + "suggestions/" + current_suggestion + '/downvote',
        type: 'PUT',
        data: user,
        success: function(data){
            //callback
        }
    });         

}

, :

:

: net:: ERR_EMPTY_RESPONSE

, 2 3 downvote . , , , , , . , - . 6 , . !

Answer 1

, $push, downvote, $addToSet . , , $addToSet . , . , $addToSet . , :

router.put('/:suggestion_id/downvote', function(req, res, next) {
    Suggestion.findByIdAndUpdate(
        req.params.suggestion_id,
        {$addToSet: {"downvote": req.body}},
        function(err, suggestion) {
            res.json(suggestion);
        }
    );
});