Fuzionest Reactjs Developer Interview Questions and Answers

React is a JavaScript library for building user interfaces that uses a virtual DOM to efficiently update the UI.

• React creates a virtual DOM to represent the UI components.

• When state or props change, React compares the virtual DOM with the actual DOM and updates only the necessary parts.

• React uses a component-based architecture to build reusable UI elements.

• React uses JSX, a syntax extension for JavaScript, to write com...read more

Redux is a predictable state container for JavaScript apps.

• Redux stores the entire state of the application in a single immutable object.

• Actions are dispatched to describe state changes.

• Reducers specify how the state changes in response to actions.

• Components can subscribe to the Redux store to access the state.

• Redux helps manage the state of complex applications and makes it easier to debug and test.

• Example: dispatchin...read more

Arrow functions are used for concise syntax, lexical scoping of 'this', and implicit return of single expressions.

• Arrow functions have a more concise syntax compared to traditional function expressions.

• Arrow functions do not bind their own 'this' value, instead they inherit 'this' from the containing scope.

• Arrow functions automatically return the result of a single expression without needing the 'return' keyword.

Destructuring syntax allows for easy extraction of values from arrays or objects in JavaScript.

• Simplifies code by providing a concise way to extract multiple values from arrays or objects

• Improves readability and maintainability of code

• Can be used in function parameters to destructure objects directly

• Example: const person = { name: 'John', age: 30 }; const { name, age } = person;

Understanding the JavaScript event loop is crucial for predicting output in asynchronous code execution.

• The event loop handles asynchronous operations in JavaScript, allowing non-blocking execution.

• JavaScript uses a call stack and a message queue to manage execution contexts.

• Example: setTimeout(() => console.log('A'), 0); console.log('B'); outputs 'B' then 'A'.

• Microtasks (like Promises) are processed before macrotas...read more

React.memo is a higher-order component that optimizes functional components by memoizing their output.

• React.memo prevents unnecessary re-renders by memoizing the component's output based on props.

• It is useful for functional components that render the same output given the same props.

• Example usage: const MemoizedComponent = React.memo(MyComponent);

• You can provide a custom comparison function as the second argument to Re...read more

Redux is a predictable state container for JavaScript apps. It helps manage the state of an application in a more organized way.

• Redux is a state management tool commonly used with React to manage the state of an application.

• It follows a unidirectional data flow, where the state is stored in a single store.

• Actions are dispatched to update the state, and reducers specify how the state should change in response to actions...read more

Context API is used in React to pass data through the component tree without having to pass props down manually at every level.

• Avoids prop drilling by providing a way to share values like themes, user data, etc. across the component tree.

• Helps in managing global state in React applications.

• Context API consists of Provider and Consumer components to provide and consume the context data.

• Can be used for theming, localizat...read more