"TypeError: Cannot read property '_id' of undefined"

[Alpgul02]

.
.
.
 let article = new Article();
    article.title = req.body.title;
    article.author = req.user._id;
    article.body = req.body.body;
.
.
.

Here in router.post('/add',....

I get the error of "TypeError: Cannot read property '_id' of undefined".

But I can correctly login with user.

How to solve this?

[techyharshit123]

_id is not a property defined by you. It is by default assigned to every entry. So it's not property but it's a key and can't be accessed like this.