A deep clone is _not_ what you want here. A correct immutable update is better described as a "nested shallow clone", where you copy each specific level of nes

A deep clone is _not_ what you want here. A correct immutable update is better described as a "nested shallow clone", where you copy each specific level of nesting from the root down to the value(s) you actually want to change. A deep clone would result in unnecessarily copying a bunch of extra objects and arrays that aren't relevant, so that's a waste of cycles. On top of that, the React ecosystem (and React-Redux in particular) relies on reference comparisons to determine if data has changed. If you copy objects that didn't actually get updated, it can cause a lot of components to re-render when they really shouldn't have. For more details see: - Dave Ceddia's "Complete Guide to Immutability in React and Redux": https://daveceddia.com/react-redux-immutability-guide/ https://daveceddia.com/react-redux-immutability-guide/ - The Redux docs page on "Immutable Update Patterns": https://redux.js.org/recipes/structuring-reducers/immutable-update-patterns https://redux.js.org/recipes/structuring-reducers/immutable-... - The Redux FAQ entry on deep cloning: https://redux.js.org/faq/performance#do-i-have-to-deep-clone-my-state-in-a-reducer-isnt-copying-my-state-going-to-be-slow https://redux.js.org/faq/performance#do-i-have-to-deep-clone... - The Redux FAQ page on immutability: https://redux.js.org/faq/immutable-data https://redux.js.org/faq/immutable-data