How to make Mongoose throw an error when pulling an entry via findByIdAndUpdate() does not find anything in the db?

Question

Hi I'm new to mongodb and node.js. I have the following abbreviated schema:

const PostSchema = new Schema({
  user: {
    type: Schema.Types.ObjectId,
    ref: 'user'
  },
  likes: [
    {
      user: {
        type: Schema.Types.ObjectId,
        ref: 'user'
      }
    }
  ],...

I want to access each Post by id (passed through request params) and then remove a like based on the user id. Presently, it removes the like from the array but does not then throw any errors when I try again to remove the same id from the db. Here is my code at the moment:

const like = await Post.findByIdAndUpdate(
      req.params.id,
      { $pull: { likes: { user: req.user.id } } },
      (error, result) => {
        if (!error) {
          return res.json('Post unliked');
        }
        return res.status(400).send('You have not liked this post');
      }
    );

Why do you want to throw an error? when there is no like to remove? — Jorge Guerra Pires, Apr 07 '20 at 21:06
Hi thanks for your reply. I suppose I don't necessarily want an error, I just want some sort of feedback that it hasn't been able to find the like from this user so I can send a different response — Finnan Holt, Apr 07 '20 at 21:15
Are you sure about this callback `(error, result)`. I took a look at a book I have about mongo, this what you are doing is mongo, no mongoose, there is no callback. — Jorge Guerra Pires, Apr 07 '20 at 21:17
https://mongoosejs.com/docs/api.html#model_Model.findByIdAndUpdate here is the doc for the mongoose function findByIdAndUpdate() — Finnan Holt, Apr 07 '20 at 21:22
One suggestion is: after you apply the function you apply, just check the size of the likes array: if it is smaller, something was removed! — Jorge Guerra Pires, Apr 07 '20 at 21:23
another option is: apply `ForEach` on the likes arrays, when you find it, remove! if you do not find it, so you can create a response. See here: https://levelup.gitconnected.com/javascript-array-some-vs-every-vs-foreach-knowledge-scoops-81dfe43369c6 — Jorge Guerra Pires, Apr 07 '20 at 21:27

score 1 · Accepted Answer · answered Apr 08 '20 at 19:12

Find the correct post with findById() instead of findByIdAndUpdate and use the higher order function map() to access the specific index of the like with the required user property.

await Post.findById(req.params.id, async (error, result) => {
      if (!error) {
        const index = result.likes
          .map(like => {
            return like.user;
          })
          .indexOf(req.user.id);

        if (index > -1) {
          console.log('found');
          //was found
          result.likes.splice(index, 1);
          await result.save();
          return res.json('Post unliked');
        } else {
          console.log('not found');
          return res.status(400).send('You have not liked this post');
        }
      }
      return res.json(error);
    });

score 0 · Answer 2 · answered Apr 07 '20 at 21:27

0

If the Id doesn't exist's then it return null so you can check if it return null then you can send the response with status 400 else you can send response with status 200. I think this can be the solution to your problem hope it work, thanks!

answered Apr 07 '20 at 21:27

Mohit Patel

11
2

"If the Id doesn't exist's then it return null ". Where does it return? o result? – Jorge Guerra Pires Apr 07 '20 at 21:30
if you console.log result you can see it – Mohit Patel Apr 07 '20 at 21:34
I am not sure about it. Result is the document, the whole document. – Jorge Guerra Pires Apr 07 '20 at 21:35
1

before removing you can check that id exist or not if if not then you can return error else success (here if the id don't exist it will return null) can check – Mohit Patel Apr 07 '20 at 21:39
indeed, it is also a nice idea! he can use something like `Every()` to make sure they are all different, or at least one is equal! – Jorge Guerra Pires Apr 07 '20 at 21:51

Jorge Guerra Pires · Answer 3 · 2020-04-07T21:48:37.477

0

Try something like this, and please let me know if it works:

 await Post.findByIdAndUpdate(
      req.params.id, (error, result) => {
        if (!error) {//if error
          return res.json(error);
        }

         const index = result.likes.indexOf(`${req.user.id}` )//find the index, I am not sure if you will need to add it as a string, make some tests!   

     if (index > -1) {//was found
       result.likes.splice(index, 1);//remove
       result.save();//save the doc to mongo
       return res.json('Post unliked');

        } 
      else  return res.status(400).send('You have not liked this post');// it was not found
      }
    );

You may need to adjust something since I am writing the code from my head!

I hope that helps!

References:

How can I remove a specific item from an array?
https://www.w3schools.com/jsref/jsref_indexof.asp
Mongoose indexOf in an ObjectId array <- this one explains that indexof do work for mongoose ids!

edited Apr 07 '20 at 21:48

answered Apr 07 '20 at 21:43

Jorge Guerra Pires

367
2
14

1

Thanks Jorge, will try this tomorrow and let you know. – Finnan Holt Apr 07 '20 at 22:38
1

Hi Jorge, this response led me to the correct answer. I had to use findById() instead of findByIdAndUpdate and I had to use the higher order function map() to access the specific index of the like with the correct user property. I'm going to update this post with the correct answer. Thanks again for your help. – Finnan Holt Apr 08 '20 at 19:07
Okay, glad to help! – Jorge Guerra Pires Apr 08 '20 at 19:20

How to make Mongoose throw an error when pulling an entry via findByIdAndUpdate() does not find anything in the db?

3 Answers3