How to get values of a field in Firestore in React

I use a document in firestore that stores three fields with boolean values. This boolean values I need for further processsing. In my programm I want to read this values. But how to read the fields of a document? As explained here it should work like following:

const getStateEntries = async () => {
  await getDoc(doc(db, 'Collection_Name', 'Document_ID'))
  .then((docSnap)=> {
    let alertField = docSnap.data['alert_state']
    console.log(alertField)
  })
  setAlertState(alertField)
}

When I run the code it looks like get no access to the field. When I print the variable to the console, I get an 'undefined'.

>Solution :

The data is not a property on DocumentSnapshot. Try refactoring the code as shown below:

let alertField = docSnap.data().alert_state