Q111. How would you create a reusable Context?
A **reusable Context** bundles the `createContext` call, its `Provider` (with local state/logic), and a custom hook to consume it into a single module. This hides the raw...
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Q112. What is the difference between client state and server state?
**Client state** is data that lives entirely in the browser and is owned by the UI — it doesn't need to be synchronized with a backend. **Server state** is data that actu...
Q113. What is normalized Redux state?
**Normalized state** stores data the way a relational database would: each type of entity is kept in a lookup table keyed by ID, instead of being nested/duplicated inside...
Q114. Why is normalized state important for performance?
1. **O(1) lookups by ID** instead of scanning/`find()`-ing through an array every time a component needs one item. 2. **Updates are localized**: changing one entity only ...
Q115. What is the Redux middleware signature?
Middleware is written as **three nested (curried) functions**: ```javascript const exampleMiddleware = (store) => (next) => (action) => { // store => { getState, dispatch...
Q116. How do you handle cross-slice communication?
Since each `createSlice` only manages its own piece of state, a few patterns let one slice react to actions or data from another: 1. **`extraReducers`**: listen for anoth...
Q117. What are Redux serializable values?
Redux (and Redux Toolkit's default middleware) expects **state and actions to contain only plain, serializable data**: strings, numbers, booleans, `null`, plain objects, ...
Q118. How do you persist Redux state?
**`redux-persist`** is the standard library for persisting and rehydrating a Redux store across page reloads/app restarts. It wraps your root reducer so selected slices a...
Q119. How do you debug a Redux performance problem?
A practical, step-by-step approach: 1. **Confirm it's actually Redux**: use the React DevTools **Profiler** to see which components re-render and how often, before assumi...
Q120. What should be stored in Redux vs derived with selectors?
A common mistake is storing **computed/derived values** in Redux state itself, which then has to be kept in sync manually every time the source data changes. The rule of ...