webdev firebase how to console.log doc().data() as a string/ how to log the value inside a field as a string?

I want to check whether a field inside a document is empty by using an if statement. I tried to use toString() such that the doc().data() becomes a string and therefore I can do stuff like (doc().data().toString() === ""). But it did not work. When I console.log doc().data().toString() it logs [object Object] whereas the actual field was empty like this "". If anyone knows how to convert the field value as a string such that it can be used like this doc().data().toString() === "") teach how to!!!