Uncaught TypeError: postData.likes is undefined in express

Hello everyone im experiencing a type error when trying to console.log the amount of likes on a post . I get postData.likes is undefined in the web dev console. Ive checked my code maybe 100 times by now and cant find a error. I checked my models and I made sure thing were properly populated and cant figure out what the issue is. Im trying to a PUT request in jquery. When I like a post in the Users mongo db document the likes array is coming up exactly as it should. Then it should also be doing the same thing in the post document but it is not. The users collection is called users and the posts collection is called posts. Im thinking the issue has to do with me using .populate I just cant figure out the problem so im hoping someone here can help.

commen.js file

$("#postTextarea").keyup((event) => {
  const textbox = $(event.target);
  const value = textbox.val().trim();

  const submitButton = $("#submitPostButton");

  if (submitButton.length == 0) return alert("No submit button found");

  if (value == "") {
    submitButton.prop("disabled", true);
    return;
  }

  submitButton.prop("disabled", false);
});

$("#submitPostButton").click(() => {
  const button = $(event.target);
  const textbox = $("#postTextarea");

  const data = {
    content: textbox.val(),
  };

  $.post("/api/posts", data, (postData) => {
    const html = createPostHtml(postData);
    $(".postsContainer").prepend(html);
    textbox.val("");
    button.prop("disabled", true);
  });
});

$(document).on("click", ".likeButton", (event) => {
  const button = $(event.target);
  const postId = getPostIdFromElement(button);

  if (postId === undefined) return;

  $.ajax({
    url: `/api/posts/${postId}/like`,
    type: "PUT",
    success: (postData) => {
      console.log(postData.likes.length);
    },
  });
});

function getPostIdFromElement(element) {
  const isRoot = element.hasClass("post");
  const rootElement = isRoot == true ? element : element.closest(".post");
  const postId = rootElement.data().id;

  if (postId === undefined) return alert("Post id undefined");

  return postId;
}

function createPostHtml(postData) {
  const postedBy = postData.postedBy;

  if (postedBy._id === undefined) {
    return console.log("User object not populated");
  }

  const displayName = postedBy.firstName + " " + postedBy.lastName;
  const timestamp = timeDifference(new Date(), new Date(postData.createdAt));

  return `<div class='post' data-id='${postData._id}'>

              <div class='mainContentContainer'>
                  <div class='userImageContainer'>
                      <img src='${postedBy.profilePic}'>
                  </div>
                  <div class='postContentContainer'>
                      <div class='header'>
                          <a href='/profile/${postedBy.username}' class='displayName'>${displayName}</a>
                          <span class='username'>@${postedBy.username}</span>
                          <span class='date'>${timestamp}</span>
                      </div>
                      <div class='postBody'>
                          <span>${postData.content}</span>
                      </div>
                      <div class='postFooter'>
                          <div class='postButtonContainer'>
                              <button>
                                  <i class='far fa-comment'></i>
                              </button>
                          </div>
                          <div class='postButtonContainer'>
                              <button>
                                  <i class='fas fa-retweet'></i>
                              </button>
                          </div>
                          <div class='postButtonContainer'>
                              <button class='likeButton'>
                                  <i class='far fa-heart'></i>
                              </button>
                          </div>
                      </div>
                  </div>
              </div>
          </div>`;
}

function timeDifference(current, previous) {
  var msPerMinute = 60 * 1000;
  var msPerHour = msPerMinute * 60;
  var msPerDay = msPerHour * 24;
  var msPerMonth = msPerDay * 30;
  var msPerYear = msPerDay * 365;

  var elapsed = current - previous;

  if (elapsed < msPerMinute) {
    if (elapsed / 1000 < 30) return "Just now";

    return Math.round(elapsed / 1000) + " seconds ago";
  } else if (elapsed < msPerHour) {
    return Math.round(elapsed / msPerMinute) + " minutes ago";
  } else if (elapsed < msPerDay) {
    return Math.round(elapsed / msPerHour) + " hours ago";
  } else if (elapsed < msPerMonth) {
    return Math.round(elapsed / msPerDay) + " days ago";
  } else if (elapsed < msPerYear) {
    return Math.round(elapsed / msPerMonth) + " months ago";
  } else {
    return Math.round(elapsed / msPerYear) + " years ago";
  }
}

Models/Posts.js

const mongoose = require("mongoose");

const Schema = mongoose.Schema;

const PostSchema = new Schema(
  {
    content: {
      type: String,
      trim: true,
    },
    postedBy: {
      type: Schema.Types.ObjectId,
      ref: "users",
      pinned: Boolean,
      likes: [{ type: Schema.Types.ObjectId, ref: "users" }],
    },
  },
  { timestamps: true }
);

const Post = mongoose.model("posts", PostSchema);
module.exports = Post;

models/User.js

const mongoose = require("mongoose");

const Schema = mongoose.Schema;

const UserSchema = new Schema(
  {
    firstName: {
      type: String,
      required: true,
      trim: true,
    },
    lastName: {
      type: String,
      required: true,
      trim: true,
    },
    username: {
      type: String,
      required: true,
      trim: true,
      unique: true,
    },
    email: {
      type: String,
      required: true,
      trim: true,
      unique: true,
    },

    password: {
      type: String,
      required: true,
    },

    profilePic: {
      type: String,
      default: "/images/default.jpeg",
    },
    likes: [{ type: Schema.Types.ObjectId, ref: "posts" }],
  },
  { timestamps: true }
);

const User = mongoose.model("users", UserSchema);
module.exports = User;

postController.js

const express = require("express");
const User = require("../../models/User");
const Post = require("../../models/Posts");

exports.handlePostRequest = async (req, res, next) => {
  if (!req.body.content) {
    console.log("content param not sent");
    return res.sendStatus(400);
  }

  const postData = {
    content: req.body.content,
    postedBy: req.session.user,
  };

  Post.create(postData)
    .then(async (newPost) => {
      newPost = await User.populate(newPost, { path: "postedBy" });

      res.status(201).send(newPost);
    })
    .catch((error) => {
      console.log(error);
      res.sendStatus(400);
    });
};

exports.handleGetRequest = async (req, res, next) => {
  await Post.find()
    .populate("postedBy")
    .sort({ createdAt: -1 }) //Shows posts by newest first
    .then((results) => {
      res.status(200).send(results);
    })
    .catch((error) => {
      console.log(error);
      res.sendStatus(400);
    });
};

exports.handlePutRequest = async (req, res, next) => {
  const postId = req.params.id;
  const userId = req.session.user._id;

  const isLiked =
    req.session.user.likes && req.session.user.likes.includes(postId);

  const option = isLiked ? "$pull" : "$addToSet";

  // Insert user like
  req.session.user = await User.findByIdAndUpdate(
    userId,
    { [option]: { likes: postId } },
    { new: true }
  ).catch((error) => {
    console.log(error);
    res.sendStatus(400);
  });

  // Insert post like
  const post = await Post.findByIdAndUpdate(
    postId,
    { [option]: { likes: userId } },
    { new: true }
  ).catch((error) => {
    console.log(error);
    res.sendStatus(400);
  });

  res.status(200).send(post);
};