Redux best practice to filter data

in the process of developing an application, I’m facing a question about whether I’m using Redux correctly. I have a fav:[] in which I add product objects and render their list. However, in order for the data not to be lost, I have to copy this fav:[] to favCopy:[] and only after that execute .filter Example code:

case "fav":
                state.fav = action.payload.filter === 'all'
                    ? state.favCopy
                    : state.favCopy.filter((item: any) => item[type] === action.payload.filter)

                break;

I would like to understand how right I am by keeping the original array intact? Maybe there is a way not to multiply arrays and use only one state?

Answer

We would recommend not doing filtering directly in the reducer most of the time. Instead, keep the original array in state as-is, and then also store a description of how you want the filtering to be done. From there, use selector functions to derive the filtered value as needed:

https://redux.js.org/usage/deriving-data-selectors