node.js mongojs findOne callback returning error as null

Question

Presently being driven up the wall by this error. I am running a node.js app with the mongojs wrapper for mongodb. I Started mongod on the default port, then ran ``` var db = require('mongojs').connect('localhost:27017/my_db'); var users = db.collection('users'); users.findOne({'fb_id' : fbUserMetadata.id}, function(err, user) { console.log(err); console.log(user); debugger; }); ``` however err and user are both 'null'. To my knowledge, err should be populated with some kind of data even if it doesn't find anything. How do I get the callback function to work properly? Pardon the newbie question.

Accepted Answer

When the `findOne` query doesn't find at least one matching document, the second parameter of the callback (in this case `user`) is set to `null`. It's not an error, so `err` is also `null`. So what you're seeing is the expected no-match-found response.

Update

Note that `findOne` has been deprecated in the 2.0 driver, but its replacement also exhibits this same behavior:

```
users.find({'fb_id' : fbUserMetadata.id}).limit(1).next(err, doc) {
    // doc is null if a matching document wasn't found
});
```

node.js mongojs findOne callback returning error as null

Solution

Problem