HCL Group Reactjs Developer Interview Questions and Answers

Closure is a feature in JavaScript that allows a function to access variables in its outer scope.

• A closure is created when a function is defined inside another function.

• The inner function has access to the outer function's variables and parameters.

• The outer function's variables and parameters are not accessible from outside the closure.

• Closures can be used to create private variables and methods.

• Example: function outer...read more

ES6 features are new additions to JavaScript language syntax and functionality.

• Arrow functions

• Template literals

• Let and const keywords

• Destructuring assignment

• Spread and rest operators

• Classes

• Modules

• Promises

• Default parameters

• Object.assign()

• Symbol data type

Hoisting is a JavaScript behavior where variable and function declarations are moved to the top of their containing scope.

• Hoisting applies to both variable and function declarations.

• Variable declarations are hoisted but not their initializations.

• Function declarations are fully hoisted, allowing them to be called before they are declared.

• Hoisting does not apply to variables declared with let or const.

• Hoisting can lead t...read more

Higher-order functions are functions that take one or more functions as arguments or return a function as their result.

• Higher-order functions can be used to create reusable code by abstracting common patterns.

• They enable functional programming paradigms like currying and composition.

• Examples of higher-order functions in JavaScript include map, filter, and reduce.

var is function scoped, let and const are block scoped.

• var can be redeclared and updated within its scope

• let can be updated but not redeclared within its scope

• const cannot be updated or redeclared once declared

• let and const are not hoisted like var

• const must be initialized during declaration

Hooks are a feature in React.js that allow developers to use state and other React features in functional components.

• Hooks are functions that let you use React features in functional components

• They allow you to use state and other React features without writing a class

• Hooks provide a way to reuse stateful logic between components

• Some commonly used hooks are useState, useEffect, and useContext

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

States are mutable data managed within a component, while props are immutable data passed from parent to child components.

• States are managed within a component and can be changed using setState method

• Props are passed from parent to child components and are immutable

• States are used for internal component data management, while props are used for passing data between components

• Example: A counter component may have a stat...read more

Data can be passed from children to parents in React components by using callback functions.

• Use callback functions to pass data from child components to parent components

• Parent component passes a function as a prop to child component

• Child component calls the function with the data as an argument to pass data to parent component