ReactJS - Managing state with useReducer and dynamic state updates without losing performance
I'm writing unit tests and I tried several approaches but none seem to work. I'm having trouble with I'm sure I'm missing something obvious here, but Hey everyone, I'm running into an issue that's driving me crazy... I am currently building a React application using hooks, specifically leveraging `useReducer` for state management. I have a complex state structure that includes an array of items, each with its own properties, and I need to update these properties dynamically based on user interactions. However, I've noticed that my application is experiencing performance optimization when updating the state, especially with large arrays. Here’s an example of my state structure: ```javascript const initialState = { items: [ { id: 1, name: 'Item 1', quantity: 0 }, { id: 2, name: 'Item 2', quantity: 0 }, // ... potentially hundreds of items ], }; const reducer = (state, action) => { switch (action.type) { case 'UPDATE_QUANTITY': return { ...state, items: state.items.map(item => item.id === action.payload.id ? { ...item, quantity: action.payload.quantity } : item ), }; default: return state; } }; ``` I am dispatching actions like so: ```javascript const updateQuantity = (id, quantity) => { dispatch({ type: 'UPDATE_QUANTITY', payload: { id, quantity } }); }; ``` Whenever I update the quantity, the entire state seems to re-render which is causing noticeable lag in the UI, especially as the number of items grows. I’ve tried wrapping the `dispatch` calls in `useCallback` to memoize the function and prevent unnecessary re-renders, but it hasn't made a important difference. I also considered using `React.memo` on individual item components to memoize their rendering based on props, but that approach seems tedious and behavior-prone as the complexity grows. I am seeing a warning in my console: `Warning: need to perform a React state update on an unmounted component.` which suggests I might be trying to update the state of a component that is no longer in the DOM. It also leads me to think I might be handling updates incorrectly. Is there a better strategy for managing complex state updates with `useReducer` while maintaining performance? Are there best practices for optimizing these types of updates in React without falling into the trap of excessive re-renders? This is my first time working with Javascript 3.11. Any suggestions would be helpful. The stack includes Javascript and several other technologies. Is there a simpler solution I'm overlooking? Any suggestions would be helpful.