Top Redux Interview Questions (2024)

1. What is Redux?
2. When to use Redux?
3. What is state management in Redux?
4. What are the 3 principles of Redux?
5. How to createStore in Redux?
6. What methods are available in the Redux Store?
7. What is combineReducers in Redux?

Q: What is Redux?
Ans:

Redux is a JavaScript library that allows you to manage the state of your application. For creating user interfaces, it is most typically used alongside libraries like React or Angular. Dan Abramov and Andrew Clark designed it in the same way that Facebook's Flux architecture was.

Redux, often known as a Redux store, is a state container for JavaScript projects. It keeps track of the app's entire state in an immutable object tree.

Q: When to use Redux?
Ans:

Redux is most beneficial in below cases:

1. If you 've got a lot of application state that you need in a lot of places in the application
2. The app state is frequently updated
3. The logic for updating that state is complicated.
4. The app's codebase is medium or huge, and many people may be working on it.
5. You must observe how that state continues to change.

Q: What is state management in Redux?
Ans:

Redux lets you manage the state of your application in one place, making updates more predictable and traceable. This usually occurs when your app reaches a point where managing app state becomes a burden, and you begin looking for ways to make it easier and simpler.

Q: What are the 3 principles of Redux?
Ans:

Below are Three Principles of Redux:

1. There is only one source of truth. Within a single store, your application's global state is kept in an object tree.
2. The state is a read-only. The only way to change the state is to perform an action, which is an object that describes what occurred.
3. Clean functions are used to make changes.

Q: How to createStore in Redux?
Ans:

It creates a Redux store that contains your app's entire state tree. A Redux Function called createStore(reducer, [initialState], [enhancer]) is used to create a new store. It has three arguments:

1. reducer (Function)

   A reducing function which returns the next state tree, by having the current state tree and an action to handle.

2. initialState

   The initial state of the store.

3. enhancer

   Can be used to improve the Redux store by incorporating third-party libraries and middleware for logging, persistent storage, and so on.

The redux-logger library is used in the following example to add console logs when the state changes. This is accomplished through the use of the applyMiddleware function:

import {createStore, applyMiddleware} from 'redux';
import createLogger from 'redux-logger';

import reducer from './reducer';

/**
 * Create a logger.
 */
const logger = createLogger();
const initialState = {};

const store = createStore(reducer, initialState, applyMiddleware(logger));

Q: What methods are available in the Redux Store?
Ans:

The Redux store API is small, with only four methods:

1. store.getState()

   Returns the current object tree's state.

2. store.dispatch(action)

   To modify the state, dispatch an action.

3. store.subscribe(listener)

   Listen to state tree changes.

4. store.replaceReducer(nextReducer)

   Replaces the existing reducer with a different reducer. This approach is utilised in more complex applications such as code splitting.

Q: What is combineReducers in Redux
Ans:

The combineReducers helper function converts an object whose values are different reducing functions into a single reducing function that can be passed to the createStore method.

The resulting reducer invokes all child reducers and collects their output into a single state object.The state created by combineReducers namespaces the states of each reducer based on the keys supplied to combineReducers()

rootReducer = combineReducers({apple: appleReducer, mango: mangoReducer})
// This would produce the following state object
{
  apple: {
    // ... apples and other state managed by the appleReducer ...
  },
  mango: {
    // ... mangoes and other state managed by the mangoReducer, maybe some juice..
  }
}