Can I check if document exists and then update it in one query?

I tried to do it like bellow with JavaScript promise, but result is always 'Your account has been activated!'.

I deleted all documents in my database, so result intantionally would be negative, but even so result is 'Your account has been activated!'

    usersCollection.findOneAndUpdate({"activationLink": activationLink}, {"$set": {"isActivated": true}}).then(function(userDoc) {
        if (userDoc) {
            console.log('Your account has been activated!')
        } else {
            console.log('This account does not exist!')
    }).catch((e) => {
        console.log(e)
    })