Step 24: Bookmark DAO with Mongoose ODM

Update the src/data/BookmarkDAO.js file:

import Bookmark from "../model/Bookmark.js";

class BookmarkDAO {
  // return the created bookmark
  async create({ title, url }) {
    const bookmark = await Bookmark.create({ title, url });
    return bookmark;
  }

  // return all bookmarks
  async readAll({ title, url }) {
    const filter = {};
    if (title) {
      filter.title = title;
    }

    if (url) {
      filter.url = url;
    }

    const bookmarks = await Bookmark.find(filter);
    return bookmarks;
  }

  // return the bookmark with the given id
  // return null if id does not exist in our database
  async read(id) {
    const bookmark = await Bookmark.findById(id);
    return bookmark;
  }

  // return the updated bookmark
  // return null if id does not exist in our database
  async update({ id, title, url }) {
    const bookmark = await Bookmark.findByIdAndUpdate(
      id,
      { title, url },
      { new: true, runValidators: true }
    );
    return bookmark;
  }

  // return the deleted bookmark
  // return null if id does not exist in our database
  async delete(id) {
    const bookmark = await Bookmark.findByIdAndDelete(id);
    return bookmark;
  }
}

export default BookmarkDAO;

Notes:

• The create method allows you to create documents of that model. As an argument, it takes an object representing the data to be saved in the database. It throws an error if it encounters any errors while creating a document.
• The find method takes an optional parameter, a filter, which can be used to search for notes that match the given attribute values. If we want to receive all notes, we can call find with no argument or with an empty filter object.
• If there are no "bookmarks" in the database, or there is no match for the filter we have provided, the find method returns an empty array.
• The first argument to findByIdAndUpdate is the ID of a bookmark in our database to be updated. If id does not match an existing bookmark, the findByIdAndUpdate will return null.
• The second argument to findByIdAndUpdate is an object containing the new attributes (and their values) which are to replace the existing attribute values of the bookmark to be updated. If any of these are undefined, the attribute will not change (so we don't need if statements to guard against this scenario)
• The third argument to findByIdAndUpdate is an “option” object. The first option is new: true which changes the default behavior of findByIdAndUpdate to return the updated note (instead of the original one). The second option is runValidators: true that changes the default behavior of findByIdAndUpdate to force running validators on new attributes. If validation fails, the findByIdAndUpdate operation throws an error.
• The findByIdAndDelete will delete and return the deleted note if the id exists in the database. Otherwise, it will return null.