MongoDB $push method seems to be not working

Question

This is my User Schema, and I'm unable to add any posts.

import mongoose from "mongoose";
const { Schema } = mongoose;

const postSchema = new Schema(
  {
    userId: {
      type: String,
      required: true,
    },
    content: {
      type: String,
      required: true,
      max: 240,
    },
    sketchUri: {
      type: String,
      default: "",
    },
  },
  { timestamps: true }
);

export const userSchema = new Schema(
  {
    name: {
      type: String,
      trim: true,
      required: true,
    },
    email: {
      type: String,
      trim: true,
      required: true,
      unique: true,
    },
    password: {
      type: String,
      min: 6,
      max: 64,
      required: true,
    },
    bio: {
      type: String,
    },
    website: {
      type: String,
    },
    posts: [postSchema],
    profile_pic: {},
  },
  { timestamps: true }
);

export default mongoose.model("User", userSchema);

And here is the code to add new posts:

const post = await User.findOneAndUpdate(
        { req.params.userId },
        {
          $push: {
            posts: {
              userId: req.user.id,
              content: req.body.thought,
              sketchUri: req.body.sketch,
            },
          },
        },
        { new: true }
      ).exec();
      res.json(post);

the res.json(post) statement here returns null.

Whenever I run this code, the backend returns a 200 status code, no errors are thrown inspite of using a try-catch block but the code isn't added anywhere in the database. Why is my $push function failing?

NOTE: Also, when I run the findOneAndUpdate function as follows, it returns the correct data, so the userId is correct.

const post = await User.findOneAndUpdate({ userId }).exec();

This is when I run the above code, but when I run it with $push, it returns null.

Answer 1

I see you are using findOneAndUpdate() and passing req.params.userId

You should be using findByIdAndUpdate() if you wish to pass the id as a parameter to find the user to update or change your code to be like:

const post = await User.findOneAndUpdate(
        { id: req.params.userId },
        {
          $push: {
            posts: {
              userId: req.user.id,
              content: req.body.thought,
              sketchUri: "aaaaaaa",
            },
          },
        },
        { new: true }
      ).exec();
      res.json(post);

I added id: req.params.userId if you can't see it