1function updateVeryNestedField(state, action) {
2 return {
3 ...state,
4 first: {
5 ...state.first,
6 second: {
7 ...state.first.second,
8 [action.someId]: {
9 ...state.first.second[action.someId],
10 fourth: action.someValue
11 }
12 }
13 }
14 }
15}