MERN Stack Middleware: Check if an :id is a valid Object type

This middleware was made for MERN stack projects.

When performing a GET request on a route that takes an :id to return a single object from a collect it is important to handle cases where the :id provided does not represent a valid object in our database.

GET http://localhost:5000/api/post/5f85294e21fcef22fd5b8f78

Here is some middleware we can create to help us do that.

const mongoose = require('mongoose');

// middleware to check for a valid object id in the url
const checkObjectId = (idToCheck) => (req, res, next) => {
  if (!mongoose.Types.ObjectId.isValid(req.params[idToCheck]))
    return res.status(400).json({ msg: 'Invalid ID' });
  next();
};

module.exports = checkObjectId;

Now we can import checkObjectId and use it in any request that takes in an :id and return an object.

// IMPORTS
const express = require('express');
const router = express.Router();
// MIDDLEWARE
const checkObjectId = require('../../middleware/checkObjectId');
// MODELS
const Post = require('../../models/Post');

// @route    GET api/posts/:id
// @desc     Get post by ID
// @access   Public
router.get(
  // ROUTE
  '/:id',
  // MIDDLEWARE
  checkObjectId('id'),
  // CALLBACK
  async (req, res) => {
    try {
      const post = await Post.findById(req.params.id);

      if (!post) {
        return res.status(404).json({ msg: 'Post not found' })
      }

      res.json(post);
    } catch (err) {
      console.error(err.message);

      res.status(500).send('Server Error');
    }
  }
);