Mongoose - Increment a value inside an array of objects

Question

I am having hard time figuring out how to increment a value in an object within an array

For instance I have this document based on Poll schema:

{
  "_id": "584b2cc6817758118e9557d8",
  "title": "Number of Skittles",
  "description": "Test1",
  "date": "Dec 9, 2016",
  "__v": 0,
  "labelOptions": [
    {
      "Bob": 112
    },
    {
      "Billy": 32
    },
    {
      "Joe": 45
    }
  ]
}

Using express, I am able to get this far:

app.put('/polls/:id', function(req, res){
  let id = req.params.id;
  let labelOption = req.query.labelOption;
  Poll.findOneAndUpdate(
    {'_id' :  id},
    {$inc: {`labelOptions.$.${labelOption}`: 1 }},
    function(err){
      console.log(err)
    })

where labelOption is the one that I would like to increment its value

To be more concise, I am having trouble transversing inside the document.

borislemke · Accepted Answer · 2016-12-10T07:56:44.083

It is not possible to directly increment the value in the .find query if labelOptions is an Array of Object. To make it easier, you should change the labelOptions type from Array of Objects to Object:

"labelOptions": {
    "Bob": 112,
    "Billy": 32,
    "Joe": 45
};

Also consider using .findByIdAndUpdate instead of .findOneAndUpdate if you are querying by the document's _id. And then, you can achieve what you want by:

Poll.findByIdAndUpdate(
    id,
    {$inc: {`labelOptions.${labelOption}`: 1 }},
    function(err, document) {
    console.log(err);
});

UPDATE: If you are persistent on using Array of Objects for labelOptions, there is a workaround:

Poll.findById(
    id,
    function (err, _poll) {

        /** Temporarily store labelOptions in a new variable because we cannot directly modify the document */
        let _updatedLabelOptions = _poll.labelOptions;

        /** We need to iterate over the labelOptions array to check where Bob is */
        _updatedLabelOptions.forEach(function (_label) {

            /** Iterate over key,value of the current object */
           for (let _name in _label) {

               /** Make sure that the object really has a property _name */
               if (_label.hasOwnProperty(_name)) {

                   /** If name matches the person we want to increment, update it's value */
                   if (_name === labelOption) ++_label._name;
               }
           }
        });

        /** Update the documents labelOptions property with the temporary one we've created */
        _poll.update({labelOptions: _updatedLabelOptions}, function (err) {

            console.log(err);
        });
    });

score 4 · Answer 2 · answered May 07 '19 at 09:16

There is another way to do this which allows a more flexible document model. If you add a field to your object like:

{
  "_id": "584b2cc6817758118e9557d8",
  "title": "Number of Skittles",
  "description": "Test1",
  "date": "Dec 9, 2016",
  "__v": 0,
  "labelOptions": [
    {
      "name": "Bob",
      "number": 112
    },
    {
      "name": "Billy",
      "number": 32
    },
    {
      "name": "Joe"
      "number": 45
    }
  ]
}

Then you can do:

app.put('/polls/:id', function(req, res){
  let id = req.params.id;
  let labelOption = req.query.labelOption;
  Poll.findOneAndUpdate(
    {
     '_id' :  id,
     'labelOptions.name
    },
    {$inc: {
      `labelOptions.$.number`: 1 
    }},
    function(err){
      console.log(err)
    })

Mongoose - Increment a value inside an array of objects

2 Answers2

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