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Ferticare Reactjs Developer Interview Questions and Answers
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1 interview found
Anonymous
(2 Questions)
- Q1. Hooks in react Useeffect hook uses
- Ans.
The useEffect hook is used in React to perform side effects in functional components.
It is used to handle side effects, such as fetching data, subscribing to events, or manually changing the DOM.
It takes two parameters: a function that contains the side effect logic, and an optional array of dependencies.
The function passed to useEffect will run after the component has rendered.
If the dependency array is provided, the ...
- Q2. How to use use context in react
- Ans.
Context is used to share data between components without passing props manually.
Create a context using createContext()
Wrap the components that need access to the context in a
component Access the context value using useContext() hook
Update the context value using the provided setter function
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Selected
I applied via Recruitment Consulltant and was interviewed in Oct 2024. There were 2 interview rounds.
(5 Questions)
- Q1. Component lifecycle
- Q2. What is DOM tree?
- Ans.
DOM tree is a hierarchical representation of HTML elements in a web page.
DOM stands for Document Object Model.
It is a tree-like structure where each node represents an HTML element.
The DOM tree is created by the browser when a web page is loaded.
It allows JavaScript to manipulate the content, structure, and style of a web page.
- Q3. What is the difference between props and state?
- Ans.
Props are immutable and passed from parent component, while state is mutable and managed within the component.
Props are read-only and cannot be modified by the component receiving them.
State is mutable and can be changed by the component that owns it.
Props are passed from parent to child components, while state is managed within the component itself.
Example: Props can be used to pass data from a parent component to a c...
- Q4. What is redux and when to use it and when not to use it?
- Ans.
Redux is a predictable state container for JavaScript apps. It is used to manage application state in a centralized way.
Use Redux when you have complex state management needs in your application.
Redux is helpful for large applications with many components that need access to the same state.
Avoid using Redux for simple applications with minimal state management requirements.
Consider using React's built-in state manageme...
- Q5. Two arrays passed to one function, then remove the elements passed from source array and present in another array
- Ans.
Remove elements from source array present in another array passed to a function
Loop through elements in source array and check if they exist in the other array
If an element is found in both arrays, remove it from the source array
(5 Questions)
- Q1. What is DOM tree
- Ans.
DOM tree is a hierarchical representation of HTML elements in a web page.
DOM stands for Document Object Model
It is a tree-like structure where each node represents an HTML element
The root node is the element, followed by
and elementsNodes can have parent-child relationships, siblings, and descendants
JavaScript can manipulate the DOM to dynamically update the content and structure of a web page
- Q2. What are lifecycle methods of react? How we can achieve same in functional components?
- Ans.
React lifecycle methods are methods that are invoked at different stages of a component's life cycle.
Some lifecycle methods include componentDidMount, componentDidUpdate, componentWillUnmount, etc.
In functional components, we can achieve similar functionality using useEffect hook.
For example, useEffect with an empty dependency array can mimic componentDidMount, while useEffect with dependencies can mimic componentDidUp
- Q3. What is redux? Explain its architecture.
- Ans.
Redux is a predictable state container for JavaScript apps.
Redux is a state management library commonly used with React.
It helps in managing the state of the application in a predictable way.
Redux follows a unidirectional data flow architecture.
Actions are dispatched to update the state, which is stored in a single immutable state tree.
Reducers are pure functions that specify how the state should change in response to
- Q4. When do we use any in typescript?
- Ans.
The 'any' type in TypeScript is used when the type of a variable is not known during development.
Use 'any' when working with dynamic data types or when the type cannot be determined at compile time.
Avoid using 'any' as much as possible to maintain type safety and improve code quality.
Consider using 'unknown' type instead of 'any' for better type checking and error prevention.
- Q5. What is the checklist for improving performance of React application?
- Ans.
Checklist for improving performance of React application
Use React.memo or PureComponent for optimizing rendering
Avoid unnecessary re-renders by using shouldComponentUpdate or React.memo
Use code splitting to load only necessary components
Optimize state management with libraries like Redux or Context API
Minimize the use of inline styles and prefer CSS stylesheets for better performance
Skills evaluated in this interview
I applied via Recruitment Consulltant and was interviewed in Sep 2024. There was 1 interview round.
(16 Questions)
- Q1. What is hosting and closer
- Ans.
Hosting is the process of storing a website or application on a server, while closure is a function that retains access to variables from its parent scope.
Hosting involves storing a website or application on a server to make it accessible on the internet.
Closure is a function that retains access to variables from its parent scope, even after the parent function has finished executing.
- Q2. What is difference between var let and const give me an explanation on what block scope
- Ans.
var, let, and const are used to declare variables in JavaScript. var has function scope, let has block scope, and const is a constant with block scope.
var has function scope, meaning it is accessible throughout the function it is declared in.
let has block scope, meaning it is only accessible within the block it is declared in.
const is similar to let in terms of block scope, but the value cannot be reassigned.
- Q3. What is asynchronous and how it works
- Ans.
Asynchronous programming allows tasks to run independently of the main program flow, improving performance and responsiveness.
Asynchronous code does not block the main thread, allowing other tasks to continue while waiting for a response.
Callbacks, promises, and async/await are common ways to handle asynchronous operations in JavaScript.
Example: fetching data from an API while the rest of the application continues to r
- Q4. Tell me the output 1)a = 20; console.log(a); var a; 2)b=10; console.log(b); let b; 3)let a =5; if(a<5){ let b = " a lessthen 5"; }else{ let b = "b is grater then 5"; } console.log(b);
- Ans.
The output for the given code snippets will be: 1) 20 2) ReferenceError: Cannot access 'b' before initialization 3) ReferenceError: b is not defined
In the first snippet, variable 'a' is declared using 'var' after it is assigned a value, so it logs 20 without any issues.
In the second snippet, variable 'b' is declared using 'let' after it is assigned a value, so it throws a ReferenceError as 'b' is accessed before initia...
- Q5. Give a div with text and display center of the page and apply animation using HTML and css
- Ans.
Centered div with text and animation using HTML and CSS
Create a div element with text inside
Apply CSS styles to center the div on the page
Use CSS animations to add animation effects
- Q6. What are semantic tags and explain
- Ans.
Semantic tags are HTML tags that provide meaning to the content they enclose, helping search engines and screen readers understand the structure of a webpage.
Semantic tags help improve SEO by providing context to search engines.
They also improve accessibility for screen readers by clearly defining the structure of a webpage.
Examples of semantic tags include
,
- Q7. How can we write responsive for web page
- Ans.
Use media queries, flexible grids, and relative units to create a responsive web page.
Use media queries to apply different styles based on screen size
Create flexible grids using CSS Grid or Flexbox
Use relative units like percentages or ems for sizing elements
Consider using frameworks like Bootstrap or Material-UI for responsive design
Test your design on different devices and screen sizes
- Q8. What is the difference between CSS and SASS? what is the use of Sass
- Ans.
SASS is a preprocessor scripting language that is interpreted into CSS, offering more features and flexibility.
SASS is a preprocessor for CSS, allowing for variables, nesting, and mixins to be used in stylesheets.
SASS code needs to be compiled into CSS before being used in a web project.
SASS helps in writing cleaner and more organized CSS code, making it easier to maintain and update styles.
CSS is the styling language ...
- Q9. Event propagation
- Q10. How would you validate the form using HTML? How do you validate the phone number with the country code?
- Ans.
Form validation can be done using HTML attributes like required, pattern, and maxlength. Phone number validation with country code can be achieved using regex.
Use the 'required' attribute to make fields mandatory
Use the 'pattern' attribute with regex to validate input format
Use the 'maxlength' attribute to limit the number of characters in a field
For phone number validation with country code, use regex to match the des...
- Q11. Which test library you use why it usecase
- Ans.
I use Jest for testing React applications due to its simplicity and integration with React ecosystem.
Jest is the most popular test library for React applications
It comes pre-configured with Create React App and has great support for snapshot testing
Jest also has built-in mocking capabilities which make it easy to test components with dependencies
- Q12. Tell me mounting and shallow concept in testing library
- Ans.
Mounting is the process of rendering a component into the DOM, while shallow rendering allows testing a component without rendering its children.
Mounting is the initial phase of the component lifecycle where the component is rendered into the DOM.
Shallow rendering in testing library renders only the component itself, not its children.
Shallow rendering is useful for isolating the component being tested and avoiding rend...
- Q13. What is redux-toolkit and what difference b/w redux and redux-toolkit
- Ans.
Redux Toolkit is the official, recommended way to write Redux logic. It simplifies the process of managing state in React applications.
Redux Toolkit provides a set of tools and best practices to streamline Redux development.
It includes utilities like createSlice, createReducer, and configureStore to simplify the code and reduce boilerplate.
Redux Toolkit also includes built-in Immer integration for writing immutable upd...
- Q14. How api call handle in redux and how can you get and display user name from redux
- Ans.
API calls in Redux are typically handled using middleware like Redux Thunk. User name can be retrieved from Redux state and displayed in components.
Use Redux Thunk middleware to make API calls in Redux
Dispatch actions to update Redux state with API response data
Access user name from Redux state in components to display it
- Q15. React hooks and how optimization
- Q16. Why we need thank in redux
- Ans.
Thunk middleware in Redux allows for asynchronous logic to be handled in Redux actions.
Thunk middleware allows for dispatching functions instead of just plain objects in Redux actions.
It enables handling asynchronous API calls within Redux actions.
Thunk middleware helps in simplifying the code by moving complex logic outside of components.
Example: Thunk middleware can be used to dispatch an action after a delay or to f...
Skills evaluated in this interview
(2 Questions)
- Q1. React basic,event loop, Lazy Loading, Suspense, Javascript basics
- Q2. Create counter application
- Ans.
Counter application using Reactjs
Create a React component for the counter
Use state to keep track of the count
Implement functions to increment and decrement the count
Display the count on the screen
I applied via LinkedIn and was interviewed in Oct 2024. There was 1 interview round.
(3 Questions)
- Q1. What are the advantages of React
- Ans.
React offers advantages such as virtual DOM for improved performance, reusable components, and easy integration with other libraries.
Virtual DOM for efficient updates and improved performance
Reusable components for easier development and maintenance
Easy integration with other libraries like Redux for state management
Support for server-side rendering for better SEO performance
- Q2. How the performance optimization can be done in React Js Application
- Ans.
Performance optimization in React Js can be achieved through code splitting, memoization, virtualization, and minimizing re-renders.
Implement code splitting to load only necessary components when needed
Use memoization techniques like useMemo and useCallback to prevent unnecessary re-renders
Implement virtualization for long lists or tables to render only visible items
Minimize re-renders by using shouldComponentUpdate or
- Q3. What is the purpose of useMemo and UseCallBack hook
- Ans.
useMemo and useCallback are hooks in React used for optimizing performance by memoizing values and functions respectively.
useMemo is used to memoize the result of a function so that it is only recomputed when its dependencies change.
useCallback is used to memoize a function instance so that it is not recreated on every render unless its dependencies change.
Both hooks help in optimizing performance by preventing unneces...
Skills evaluated in this interview
anjali rastogi
(1 Question)
- Q1. What is client side and server side rendering
(2 Questions)
- Q1. Flat the array without using the inbuilt methods
- Ans.
Flatten an array without using inbuilt methods
Use recursion to iterate through the array and flatten it
Create a new array to store the flattened elements
Check if each element is an array, if so, recursively call the function to flatten it
- Q2. Sort the given objects based on the ages
(2 Questions)
- Q1. What do you mean by redux and how to use redux
- Ans.
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...
- Q2. What is the use of Context Api in React
- Ans.
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
Skills evaluated in this interview
Niharika Thakur
I applied via Company Website and was interviewed in Jun 2024. There were 2 interview rounds.
Got a link on mail to give online clearance test. 25 questions on react, Js and html-css
(1 Question)
- Q1. Build a login page
Selected
I applied via Naukri.com and was interviewed before Aug 2023. There was 1 interview round.
(2 Questions)
- Q1. What is the difference between states and props ?
- Ans.
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...
- Q2. How are data passed from children to parents in react component?
- Ans.
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
Interview Preparation Tips
- React.Js
- HTML
- CSS
- Javascript
Skills evaluated in this interview
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