Why is immutability important in redux, and how is it achieved?

In Redux, immutability means you never change the state directly — instead, you always return a new copy of it.

Why is it important?

• Predictable updates – Reducers stay pure and easier to debug.
• Performance – Redux checks changes with ===. If you mutate state, it may not detect updates, and your UI won’t refresh.
• Time-travel debugging – DevTools can keep a history of states only if each update is immutable.

How do we achieve it?

• Use the spread operator instead of mutating:
  return { ...state, count: state.count + 1 };
• For arrays, create new ones:
  return { ...state, todos: [...state.todos, newTodo] };
• Use Redux Toolkit (Immer) to write simpler code:
  addTodo: (state, action) => { state.push(action.payload); // Looks like mutation but is safe }
  

In short: Don’t change state directly. Always return a new one. This keeps Redux fast, reliable, and easy to debug.