Firestore - batch.add is not a function
The documentation for Firestore batch writes lists only set(), update() and delete() as permitted operations.
Is there no way to add an add() operation to the batch? I need a document to be created with an auto-generated id.
Answer
You can do this in two steps:
// Create a ref with auto-generated ID
var newCityRef = db.collection('cities').doc();
// ...
// Add it in the batch
batch.set(newCityRef, { name: 'New York City' });
The .doc() method does not write anything to the network or disk, it just makes a reference with an auto-generated ID you can use later.