How to query a single field of a document in firestore firebase?

firebase

#1

example I added this document in collection

PostCollection.add({
			  name: "San Francisco",
			  state: "CA",
			  country: "USA",
			  capital: false,
			  population: 860000,
			  location: firebase.firestore().GeoPoint(4.34, 5.67)
			}).then(documentRef => {
			  console.log(`San Francisco added with auto-generated ID: ${documentRef.id}`);
			});

then I want to query the document but only want the the value of “name”.
how do I modify this code to achieve the above?

PostCollection.get().then(querySnapshot => {
			  querySnapshot.forEach(doc => {
			    console.log(`${doc.id} => ${JSON.stringify(doc.data())}`);
  });
});