Set variable equal to mongodb key value

var userLat = db.collection('users', function (err, document){
    document.findOne({_id: loggedUserID}, function(err, docs) {

    console.log(docs.currentUserLat);
});

This is my code, I'm trying to get the value that's console logged into the variable. I just can't find the correct syntax to do this. The console log does return the correct value just need to drop it into the variable. Grateful for some help.