10+ NeoSOFT Reactjs Developer Interview Questions and Answers

rem and em are both units in CSS for defining font sizes, with rem being relative to the root element and em being relative to the parent element.

• rem stands for 'root em' and is relative to the font size of the root element (usually the tag)

• em stands for 'element em' and is relative to the font size of the parent element

• To hide something in CSS, you can use the display property with a value of 'none' or the visibility property with a value of 'hidden'

• Example: To hide an eleme...read more

get props is used to retrieve the value of a property in React components, while set props is used to update the value of a property.

• get props is used to access the value of a property passed down from a parent component

• set props is used to update the value of a property in the current component

• Example: get props - accessing the 'name' prop in a child component: this.props.name

• Example: set props - updating the 'count' prop in a child component: this.props.setProps({ count: 10...read more

get forEach is used to iterate over elements in an array without returning a new array, while map creates a new array by applying a function to each element.

• forEach does not return a new array, while map returns a new array with the results of applying a function to each element

• forEach is used for side effects, while map is used for transforming data

• forEach does not return anything, while map returns a new array

• Example: const numbers = [1, 2, 3]; numbers.forEach(num => consol...read more

Hooks are a new feature in React 16.8 that allow you to use state and other React features without writing a class.

• Hooks are functions that let you use state and other React features in functional components.

• They allow you to reuse stateful logic without changing your component hierarchy.

• Some built-in hooks include useState, useEffect, useContext, etc.

• Hooks provide a more direct API to the React concepts you already know.

• They make it easier to share logic across components, a...read more

Pure component is a class component that does not re-render if the input props and state remain the same.

• Pure components implement shouldComponentUpdate method with shallow prop and state comparison.

• They are optimized for performance as they prevent unnecessary re-renders.

• Example: class MyComponent extends React.PureComponent { // component code here }

Modules in JavaScript are reusable pieces of code that can be exported from one file and imported into another.

• Modules help in organizing code into separate files for better maintainability.

• Modules can be imported using 'import' keyword and exported using 'export' keyword.

• Modules can be used to encapsulate code and prevent global namespace pollution.

• CommonJS and ES6 modules are two popular module systems in JavaScript.

Local storage is persistent and stays until manually cleared, while session storage is temporary and cleared when the browser is closed.

• Local storage data persists even after closing the browser

• Session storage data is cleared when the browser is closed

• Both store data as key-value pairs similar to cookies

Promises are objects representing the eventual completion or failure of an asynchronous operation, while async/await is a syntactic sugar built on top of promises to write asynchronous code in a synchronous manner.

• Promises are used to handle asynchronous operations and provide a way to chain multiple asynchronous operations together.

• Async/await allows you to write asynchronous code that looks synchronous, making it easier to read and maintain.

• Async functions always return a p...read more

throw is used to throw an exception, new throw is used to throw an exception with a new object

• throw is used to throw an exception in JavaScript

• new throw is used to throw an exception with a new object

• Example: throw new Error('Something went wrong')

PUT is used to update or replace an entire resource, while PATCH is used to update or modify part of a resource.

• PUT is idempotent, meaning multiple identical requests will have the same effect as a single request.

• PATCH is not necessarily idempotent, as multiple identical requests may have different effects.

• PUT requires the client to send the entire updated resource, while PATCH only requires the client to send the specific changes to be made.

• PUT is typically used when the cli...read more

Validation in React can be added using form validation libraries, custom validation functions, or built-in HTML5 validation attributes.

• Use form validation libraries like Formik or Yup for easy validation setup

• Create custom validation functions to validate input fields based on specific requirements

• Utilize built-in HTML5 validation attributes like required, pattern, and min/max for basic validation

• Display error messages based on validation results to provide feedback to users