mongoose findOneAndUpdate deletes nested vars

Question

In my express/mongoose code when I update a nested var it deletes any other nested vars in the object I didn't update?

My schema:

var MySchema = new Schema({
  active: { type: Boolean, required: true, default: true },
  myvar: {
    useDefault: { type: Boolean, required: true },
    custom: { type: String },
    default: { type: String }
  }
});

My express middleware update function:

var updateData = req.body;
MySchema.findOneAndUpdate({ active: true }, updateData, function(err, myschema) {
    if (err) throw err;
    if (!myschema) { response(403, { success:false, message: "myschema not updated." }, res); }
    // success
    response(200, { success:true, message: "myschema updated." }, res);
});

The record initially look like this:

{
    "myvar": {
        "useDefault": true,
        "custom": "some custom var",
        "default": "some value"
    }
}

When I submit an update to say the myvar.useDefault value the record ends up like this:

{
    "myvar": {
        "useDefault": false
    }
}

Can anyone advise how to update only the targeted var and leave any other vars as they were?

Answer 1

The answer was to convert the response.body object to dot notation and pass that modified object to mongoose findOneAndUpdate. Thanks to @btkostner on Gitter for the answer and his toDot function. Here is the relevant bits of code:

function(req, res) {
  // convert response to dot notation so objects retain other values
  var dotData = toDot(req.body, '.');
  MySchema.findOneAndUpdate({ active: true }, dotData, function(err, myschema) {
    ...
}

// author: @btcostner 
function toDot (obj, div, pre) {
  if (typeof obj !== 'object') {
    throw new Error('toDot requires a valid object');
  }
  if (pre != null) {
    pre = pre + div;
  } else {
    pre = '';
  }
  var iteration = {};
  Object.keys(obj).forEach(function(key) {
    if (_.isPlainObject(obj[key])) {
      Object.assign(iteration, _this.toDot(obj[key], div, pre + key));
    } else {
      iteration[pre + key] = obj[key];
    }
  });
  return iteration;
};

NOTE: I had to convert the toDot() function to ES5 for my project, here is the original ES6 version: github.com/elementary/houston/blob/master/src/lib/helpers/dotNotation.js