• What is the difference between setState and replaceState methods?
• How to listen to state changes?
• What is the recommended approach of removing an array element in react state?
• Is it possible to use React without rendering HTML?
• How to pretty print JSON with React?
• Why you can't update props in React?
• How to focus an input element on page load?
• What are the possible ways of updating objects in state?
• How can we find the version of React at runtime in the browser?
• What are the approaches to include polyfills in your create-react-app?
• How to use https instead of http in create-react-app?
• How to avoid using relative path imports in create-react-app?
• How to add Google Analytics for react-router?
• How to update a component every second?
• How do you apply vendor prefixes to inline styles in React?
• How to import and export components using react and ES6?
• What are the exceptions on React component naming?
• Why is a component constructor called only once?
• How to define constants in React?
• How to programmatically trigger click event in React?
• Is it possible to use async/await in plain React?
• What are the common folder structures for React?
• What are the popular packages for animation?
• What is the benefit of styles modules?
• What are the popular React-specific linters?
• How to make AJAX call and In which component lifecycle methods should I make an AJAX call?
• What are render props?

React Router

• What is React Router?
• How React Router is different from history library?
• What are the components of React Router v4?
• What is the purpose of push and replace methods of history?
• How do you programmatically navigate using React router v4?
• How to get query parameters in React Router v4
• Why you get "Router may have only one child element" warning?
• How to pass params to history.push method in React Router v4?
• How to implement default or NotFound page?
• How to get history on React Router v4?
• How to perform automatic redirect after login?

React Internationalization

• What is React-Intl?
• What are the main features of React Intl?
• What are the two ways of formatting in React Intl?
• How to use FormattedMessage as placeholder using React Intl?
• How to access current locale with React Intl
• How to format date using React Intl?

React Testing

• What is Shallow Renderer in React testing?
• What is TestRenderer package in React?
• What is the purpose of ReactTestUtils package?
• What is Jest?
• What are the advantages of Jest over Jasmine?
• Give a simple example of Jest test case

React Redux

• What is Flux?
• What is Redux?
• What are the core principles of Redux?
• What are the downsides of Redux compared to Flux?
• What is the difference between mapStateToProps() and mapDispatchToProps()?
• Can I dispatch an action in reducer?
• How to access Redux store outside a component?
• What are the drawbacks of MVW pattern
• Are there any similarities between Redux and RxJS?
• How to dispatch an action on load?
• How to use connect from React Redux?
• How to reset state in Redux?
• What's the purpose of at symbol in the redux connect decorator?
• What is the difference between React context and React Redux?
• Why are Redux state functions called reducers?
• How to make AJAX request in Redux?
• Should I keep all component's state in Redux store?
• What is the proper way to access Redux store?
• What is the difference between component and container in React Redux?
• What is the purpose of the constants in Redux?
• What are the different ways to write mapDispatchToProps()?
• What is the use of the ownProps parameter in mapStateToProps() and mapDispatchToProps()?
• How to structure Redux top level directories?
• What is redux-saga?
• What is the mental model of redux-saga?
• What are the differences between call and put in redux-saga
• What is Redux Thunk?
• What are the differences between redux-saga and redux-thunk
• What is Redux DevTools?
• What are the features of Redux DevTools?
• What are Redux selectors and Why to use them?
• What is Redux Form?
• What are the main features of Redux Form?
• How to add multiple middlewares to Redux?
• How to set initial state in Redux?
• How Relay is different from Redux?
• What is an action in Redux?

Miscellaneous

• What are the main features of reselect library?
• Give an example of reselect usage?
• Does the statics object work with ES6 classes in React?
• Can Redux only be used with React?
• Do you need to have a particular build tool to use Redux?
• How Redux Form initialValues get updated from state?
• How React PropTypes allow different type for one prop?
• Can I import an SVG file as react component?
• Why are inline ref callbacks or functions not recommended?
• What is render hijacking in React?
• What are HOC factory implementations?
• How to pass numbers to React component?
• Do I need to keep all my state into Redux? Should I ever use react internal state?
• What is the purpose of registerServiceWorker in React?
• What is React memo function?
• What is React lazy function?
• How to prevent unnecessary updates using setState?
• How do you render Array, Strings and Numbers in React 16 Version?
• How to use class field declarations syntax in React classes?
• What are hooks?
• What rules need to be followed for hooks?
• How to ensure hooks followed the rules in your project?
• What are the differences between Flux and Redux?
• What are the benefits of React Router V4?
• Can you describe about componentDidCatch lifecycle method signature?
• In which scenarios error boundaries do not catch errors?
• Why do you not need error boundaries for event handlers?
• What is the difference between try catch block and error boundaries?
• What is the behavior of uncaught errors in react 16?
• What is the proper placement for error boundaries?
• What is the benefit of component stack trace from error boundary?
• What is the required method to be defined for a class component?
• What are the possible return types of render method?
• What is the main purpose of constructor?
• Is it mandatory to define constructor for React component?
• What are default props?
• Why should not call setState in componentWillUnmount?
• What is the purpose of getDerivedStateFromError?
• What is the methods order when component re-rendered?
• What are the methods invoked during error handling?
• What is the purpose of displayName class property?
• What is the browser support for react applications?
• What is the purpose of unmountComponentAtNode method?
• What is code-splitting?
• What is the benefit of strict mode?
• What are Keyed Fragments?
• Does React support all HTML attributes?
• What are the limitations with HOCs?
• How to debug forwardRefs in DevTools?
• When component props defaults to true?
• What is NextJS and major features of it?
• How do you pass an event handler to a component?
• Is it good to use arrow functions in render methods?
• How to prevent a function from being called multiple times?
• How JSX prevents Injection Attacks?
• How do you update rendered elements?
• How do you say that props are read only?
• How do you say that state updates are merged?
• How do you pass arguments to an event handler?
• How to prevent component from rendering?
• What are the conditions to safely use the index as a key?
• Is it keys should be globally unique?
• What is the popular choice for form handling?
• What are the advantages of formik over redux form library?
• Why do you not required to use inheritance?
• Can I use web components in react application?
• What is dynamic import?
• What are loadable components?
• What is suspense component?
• What is route based code splitting?
• Give an example on How to use context?
• What is the purpose of default value in context?
• How do you use contextType?
• What is a consumer?
• How do you solve performance corner cases while using context?
• What is the purpose of forward ref in HOCs?
• Is it ref argument available for all functions or class components?
• Why do you need additional care for component libraries while using forward refs?
• How to create react class components without ES6?
• Is it possible to use react without JSX?
• What is diffing algorithm?
• What are the rules covered by diffing algorithm?
• When do you need to use refs?
• Is it prop must be named as render for render props?
• What are the problems of using render props with pure components?
• How do you create HOC using render props?
• What is windowing technique?
• How do you print falsy values in JSX?
• What is the typical use case of portals?
• How do you set default value for uncontrolled component?
• What is your favorite React stack?
• What is the difference between Real DOM and Virtual DOM?
• How to add Bootstrap to a react application?
• Can you list down top websites or applications using react as front end framework?
• Is it recommended to use CSS In JS technique in React?
• Do I need to rewrite all my class components with hooks?
• How to fetch data with React Hooks?
• Is Hooks cover all use cases for classes?
• What is the stable release for hooks support?
• Why do we use array destructuring (square brackets notation) in useState?
• What are the sources used for introducing hooks?
• How do you access imperative API of web components?
• What is formik?
• What are typical middleware choices for handling asynchronous calls in Redux?
• Do browsers understand JSX code?
• Describe about data flow in react?
• What is react scripts?
• What are the features of create react app?
• What is the purpose of renderToNodeStream method?
• What is MobX?
• What are the differences between Redux and MobX?
• Should I learn ES6 before learning ReactJS?
• What is Concurrent Rendering?
• What is the difference between async mode and concurrent mode?
• Can I use javascript urls in react16.9?
• What is the purpose of eslint plugin for hooks?
• What is the difference between Imperative and Declarative in React?
• What are the benefits of using typescript with reactjs?
• How do you make sure that user remains authenticated on page refresh while using Context API State Management?
• What are the benefits of new JSX transform?
• How does new JSX transform different from old transform?
• How do you get redux scaffolding using create-react-app?
• What are React Server components?
• What is prop drilling?
• What is state mutation and how to prevent it?
• What is the difference between useState and useRef hook?