Firebase firestore remove item from array of field

I am using Firebase Firestore to make my website

As you can see, I have a field commentList and its type is array and now I want to remove the first item of the array which contains a property comment: the first comment

This is what I did:

exports.delete__comment = (req, res, next) => {
  const {id} = req.params;
  const {comment} = req.body;

  return db
    .collection('instagram__posts')
    .doc(id)
    .update({
      commentList: FieldValue.arrayRemove(JSON.stringify(comment)),
    })
    .then((doc) => {
      console.log('comment deleted', comment);
      next();
    })
    .catch((err) => {
      res.status(500).json({err});
      console.log(err);
    });
};

if the item was deleted, I will console.log('comment deleted', comment); and it worked

but the sad thing is it does not remove in the database for me instead, it still there. Please show me how to fix it, thank you so much and Merry Chirstmas