Safertek It Solutions Front end Engineer Interview Questions and Answers

Very hard Apptitute

Hard javascript coding questions

Q1. Css flexbox and grid
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Q2. Pagination on scroll
Ans. 
Implementing pagination on scroll allows for loading more content as the user reaches the bottom of the page.
• Use a scroll event listener to detect when the user has reached the bottom of the page

• Make an API call to fetch more data when the bottom is reached

• Append the new data to the existing content on the page
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Q3. Immediately invoked fn and anonymous fn
Ans. 
Immediately invoked function expressions (IIFE) are functions that are executed immediately after they are created.
• IIFE is defined and invoked at the same time using parentheses at the end of the function declaration.

• Anonymous functions do not have a name and can be used as IIFE by wrapping them in parentheses.

• IIFE is commonly used to create a private scope for variables and functions.
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Q4. What are closures
Ans. 
Closures are functions that have access to variables from their outer scope even after the outer function has finished executing.
• Closures allow functions to access variables from their parent function even after the parent function has returned

• They help in creating private variables and functions in JavaScript

• Closures are commonly used in event handlers and callbacks
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Q5. What is promise? explain
Ans. 
A promise is an object representing the eventual completion or failure of an asynchronous operation.
• Promises are used to handle asynchronous operations in JavaScript.

• They can be in one of three states: pending, fulfilled, or rejected.

• Promises can be chained using .then() method to handle success and failure callbacks.

• Example: Fetch API returns a promise when making an HTTP request.
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Q6. What is lazy loading -explain
Ans. 
Lazy loading is a technique used in web development to defer loading non-essential resources until they are needed.
• Lazy loading helps improve page load times by only loading resources when they are required.

• It is commonly used for images, videos, and other media files on a webpage.

• Lazy loading can be implemented using JavaScript libraries like Intersection Observer or by using native browser features like loading='lazy
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Q7. Media query and css selectors
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Q1. Discussion about my previous project
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Q2. Question on html, css, javascript & react
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Q3. Explain about promises
Ans. 
Promises are objects representing the eventual completion or failure of an asynchronous operation.
• Promises are used to handle asynchronous operations in JavaScript.

• They can be in one of three states: pending, fulfilled, or rejected.

• Promises can be chained using .then() to handle success and .catch() to handle errors.

• Example: const myPromise = new Promise((resolve, reject) => { ... });
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Q4. Use state, context api
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Q5. Box modelling in css, css pre processors
Ans. 
Box model in CSS refers to the way elements are rendered in a web page. CSS preprocessors like SASS or LESS help streamline CSS development.
• Box model in CSS includes content, padding, border, and margin.

• CSS preprocessors like SASS or LESS allow for variables, nesting, and mixins to be used in CSS.

• Example: box-sizing: border-box; in CSS changes the box model to include padding and border in the element's total width and
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Coding test was the first round of interview

Q1. What is virtual dom in react and what makes it faster ?
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Q1. It was HR round
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Online Hackathon test was taken.

Q1. Tell Me About Yourself.
Ans. 
I am a passionate React Js Frontend Developer with experience in building user-friendly and responsive web applications.
• Experienced in developing web applications using React Js

• Proficient in HTML, CSS, and JavaScript

• Familiar with state management libraries like Redux

• Strong understanding of responsive design principles

• Ability to work collaboratively in a team environment
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Q2. Tell me about your roles and responsibilities in your current project.
Ans. 
I am responsible for developing and maintaining the frontend of the project using React Js.
• Developing user-friendly interfaces using React Js

• Implementing responsive design and ensuring cross-browser compatibility

• Collaborating with backend developers to integrate frontend with backend services

• Optimizing application performance and troubleshooting issues

• Participating in code reviews and providing feedback to team members
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Q3. How we implement SSR in React.
Ans. 
SSR in React is implemented using server-side rendering to pre-render React components on the server before sending them to the client.
• Use libraries like Next.js or Gatsby to implement SSR in React.

• Configure server to render React components on the server side.

• Optimize server-side rendering for performance by caching rendered components.
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Q4. How can we change our project in production mode from development mode.
Ans. 
To change a React project from development mode to production mode, you need to build the project using the 'npm run build' command.
• Run 'npm run build' command in the terminal to create a production build of the project.

• This command will generate a 'build' folder with optimized and minified files for production.

• You can then deploy the contents of the 'build' folder to a web server for production use.
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Q5. What is lazy loading and how we can implement in our project.

Ans. 

Lazy loading is a technique used to defer loading non-essential resources until they are needed.

• Lazy loading helps improve performance by only loading resources when they are required.

• In React, lazy loading can be implemented using React.lazy() and Suspense components.

• Example: const MyComponent = React.lazy(() => import('./MyComponent'));

• Example: Loading...

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