Mongoose find and update json in json

Question

I'm sorry if title isn't clear I didn't know how else to put this.

Let's say I have the following schema:

{
  name: {
    type: String
  },
  additionalInfo: {
    someInfo: {
      a: {
        type: String
      },
      b : {
        type: String
      }
    }
  }
}

Now say I want to make a function that changes field b and ONLY b .

function changeB(id, newB) {
  return new Promise((resolve, reject) => {
    myModel.findByIdAndUpdate(id, { additionalInfo: { someInfo: { b } } }, (err, doc) => {
      if(err) reject(err);
      if(doc) resolve(doc);
      reject();
    });
  });
}

Problem here is that function overwrites entire additionalInfo for that document. So if I had a a value in it as well, after running that function it'll be gone. What should I do to only change additionalInfo.someInfo.b ?

Answer 1

Actually while writing this question (especially on that last sentence) I figured it out myself. Following function only changes additionalInfo.someInfo.b without deleting anything else.

function changeB(id, newB) {
  return new Promise((resolve, reject) => {
    myModel.findByIdAndUpdate(id, { 'additionalInfo.someInfo.b': newB }, (err, doc) => {
      if(err) reject(err);
      if(doc) resolve(doc);
      reject();
    });
  });
}