Main reducer for react-redux-firebase. This function is called
automatically by redux every time an action is fired. Based on which action
is called and its payload, the reducer will update redux state with relevant
changes. firebaseReducer is made up of multiple "slice reducers"
(outlined in reducers docs) combined using
combineReducers
following the patterns outlined in
the redux docs.
Parameters
stateObject Current Firebase Redux State (state.firebase)actionObject Action which will modify state
Returns Object Firebase redux state