MongoDB: Why doesn't this stored JS function return a value?

Question

Consider this dummy function:

db.system.js.save({
    _id:"findId", 
    value:function(){
        var doc = db.test.find({"_id": "1"})
        return doc['_id']
    }
    })

When running it, I get nothing in return.

However, if I just return db.test.find({"_id": "1"}) I do get the document.

What's the difference?

The broader question: Can I execute arbitrary JS code on server-side?

For example, I'd like to retrieve a document and have some if-else logic

NeNaD · Accepted Answer · 2021-06-05 11:46:21Z

1

db.test.find({"_id": "1"}) returns Promise, and you are not waiting for it to resolve before returning the data. So, when you return doc['_id'], doc is undefined. So, you should return the value after the Promise resolves. You can do it like this:

db.test.find({"_id": "1"}).then((document) => {
  return document .id;
})

edited Jun 5, 2021 at 11:46

answered Jun 5, 2021 at 11:05

NeNaD

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