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Question

I have create a schema named "Process", which include some objects; some of them are not required in POST.

So I made some documents that have 'ParentrProcess' object and some without it.

I want to delete the document that with the following:

I'll check the id that in the url:

Process.findOne({ _id: req.params.id }, function (err, obj)   

If id is valid I want to search again in all documents to find if this Process._id is a ParentrProcess._id in any other documents

if false: delete the document

if true: I had 2 situations:

1. return error message 'You can not delete Process that contain Subprocess'

2. delete the documents and all related documents (Process & ParentrProcess)

Answer 1

Process.findById(req.params.id )
    .exec()
    .then(doc => {
        console.log("to database", doc);
        if (doc) {
            res.status(200).json({
                process: doc,
            });
        } else {
            res.status(404)
                .json({ message: "No valid entry found for provided ID" });
        }
    })
    .catch(err => {
        console.log(err);
        res.status(500).json({ error: err });
    });
});

Follow this code. You might reach where you want to.

Answer 2

router.post("/:processId/",  (req, res) => {
    const process = new Process({
            _id: new mongoose.Types.ObjectId(),
                name: req.body.name,
                ...

                parentId: req.params.parentId // you can add only the required fields
            });
           process.save()

        .then(result => {
            console.log(result);
            res.status(201).json({
                message: "Posted successfully",
                createdprocess: {
                    name: result.name,
                    ...
                    parentId: result.parentId
                }
            });
            Process.findOneAndUpdate({ _id: result.parenttId},
                { $push: { parentProcess:  result._id} }, // use $push to update, $pull to remove.
                function (error, success) {
                    if (error) {
                        console.log(error);
                    } else {
                        console.log(success);
                    }
                });   

        })
        .catch(err => {
            console.log(err);
            res.status(500).json({
                error: err
            });
        });
});

Well i didnt understood your complete problem, but im guessing your need is close to this.