70+ Senior Front end Developer Interview Questions and Answers

Refactored a large codebase by breaking it down into smaller modules, improving readability and maintainability.

• Analyzed the existing codebase to identify redundant or inefficient code

• Broke down the code into smaller, more manageable modules

• Implemented design patterns such as MVC or MVVM to improve code structure

• Refactored code incrementally, testing each change to ensure functionality was not affected

• Documented changes and updated comments to improve code readability

Pipe is a feature in Angular that allows you to transform data in templates. Pure pipes are called only when a pure change to the input is detected, while impure pipes are called every time change detection runs.

• Pipe is a feature in Angular used to transform data in templates

• Pure pipes are called only when a pure change to the input is detected

• Impure pipes are called every time change detection runs

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

• Lazy loading helps improve performance by only loading resources when required

• In Angular, lazy loading is achieved by creating separate modules for different parts of the application

• Lazy loading is implemented using the loadChildren property in the route configuration

Integrated complex front-end features with a back-end system in a challenging project.

• Developed a real-time chat feature using WebSockets to communicate with the back-end server

• Faced challenges with data synchronization and ensuring seamless updates across all clients

• Implemented RESTful APIs to fetch and update data from the back-end

• Used Redux for state management to handle complex data flows

• Performed thorough testing and debugging to ensure smooth integration

Optimizing web application performance involves various strategies like minification, caching, lazy loading, and image optimization.

• Minify CSS, JavaScript, and HTML files to reduce file sizes and improve load times.

• Implement browser caching to store static resources locally and reduce server requests.

• Utilize lazy loading to defer loading of non-essential resources until they are needed.

• Optimize images by resizing, compressing, and using modern image formats like WebP.

• Reduce H...read more

I handle cross-browser compatibility by testing on multiple browsers, using polyfills, and CSS resets.

• Test on multiple browsers to identify and fix issues

• Use polyfills to provide missing functionality in older browsers

• Utilize CSS resets to ensure consistent styling across browsers

• Example: Had to fix layout issues in Internet Explorer by adjusting CSS properties

I use Git for version control and collaborate with team members through branches and pull requests.

• Utilize Git for version control to track changes and collaborate with team members

• Create separate branches for different features or bug fixes to prevent conflicts

• Regularly pull changes from the main branch to stay up to date with the latest code

• Resolve code conflicts by communicating with team members and carefully merging changes

• Use pull requests for code reviews and to ensure...read more

I stay updated by following industry blogs, attending conferences, and experimenting with new technologies. I evaluate new technologies based on their benefits, community support, and compatibility with current stack.

• Follow industry blogs and websites like CSS-Tricks, Smashing Magazine, and A List Apart

• Attend conferences and meetups to learn about new technologies and best practices

• Experiment with new technologies by building small projects or prototypes

• Evaluate new technolog...read more

Key considerations for implementing responsive design include fluid grids, flexible images, media queries, and testing across various devices.

• Use fluid grids to ensure content adapts to different screen sizes

• Utilize flexible images that scale appropriately

• Implement media queries to apply different styles based on screen size

• Test the design across multiple devices to ensure consistent user experience

Implement a feature in React to display the character and count of characters on UI on each keystroke.

• Use state to store the input value and update it on each keystroke.

• Use a function to count the characters in the input value and display the result on the UI.

• Use event listeners to detect keystrokes and trigger the character count update.

Flex is a CSS layout model that allows responsive and flexible design. Hoisting is a JavaScript behavior where variable and function declarations are moved to the top of their scope. Function expressions are anonymous functions assigned to variables.

• Flex is used for creating responsive and flexible layouts in CSS.

• Hoisting in JavaScript moves variable and function declarations to the top of their scope.

• Function expressions are anonymous functions assigned to variables, like co...read more

Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine that allows developers to run JavaScript code outside of a web browser.

• Node.js is a server-side platform that uses an event-driven, non-blocking I/O model.

• It allows developers to write server-side code using JavaScript, traditionally a client-side language.

• Node.js can be used to build web servers, APIs, and other backend services.

• By using Node.js, developers can run JavaScript code on the server side, enab...read more

To create a theme in Magento 2, use the theme development process. For multi-site concept, create a new website and store view.

• Use the theme development process to create a new theme in Magento 2

• Create a new website and store view for multi-site concept

• Assign the theme to the store view

• Customize the theme using CSS and LESS

• Use the Magento 2 documentation for more information

Slice method returns a shallow copy of a portion of an array into a new array, while splice method changes the contents of an array by removing or replacing existing elements.

• Slice method does not modify the original array, while splice method does

• Slice method takes two arguments - start and end index, while splice method takes three arguments - start index, number of elements to remove, and optional elements to add

• Example of slice method: let arr = [1, 2, 3, 4, 5]; let newAr...read more

I have used features like semantic tags, forms, tables, and multimedia elements in HTML.

• Semantic tags like

  ,

• Forms for user input with

  , ,

• Tables for organizing data with

  , ,

  Multimedia elements like ,

layout.xml is used to modify the layout of a webpage. It defines the structure of the page.

• Modify the layout of a webpage using layout.xml by defining the structure of the page

• Use layout.xml to specify the position and size of elements on the page

• Add or remove elements from the page using layout.xml

• Modify the styling of elements using layout.xml

States and props are important concepts in React for managing and passing data between components.

• States are mutable data that can be changed within a component

• Props are read-only data passed from parent to child components

• States are managed within a component using setState() method

• Props are accessed using this.props in a component

Designing Jira Dashboard and WhatsApp HLD

• For Jira Dashboard, focus on displaying project status, issue tracking, and team performance metrics

• For WhatsApp HLD, consider features like messaging, voice and video calls, group chats, and file sharing

• Ensure user-friendly interface and seamless navigation for both applications

Yes, I have experience developing websites for physically challenged individuals with a focus on accessibility.

• Implemented keyboard navigation for users with mobility impairments

• Utilized ARIA roles and attributes to improve screen reader compatibility

• Ensured color contrast and text size met WCAG standards

• Tested websites with assistive technologies like screen readers and voice recognition software

Multiple language support in M2 can be added by creating language packs and configuring store views.

• Create language packs for each language to be supported

• Configure store views for each language

• Translate all text strings in the theme and extensions

• Use language switcher to allow users to switch between languages

Employee details can be retrieved using group by clause in SQL.

• Use GROUP BY clause in SQL to group employee details based on a specific column

• Aggregate functions like COUNT, SUM, AVG can be used with GROUP BY to get summarized employee details

• Example: SELECT department, COUNT(*) as total_employees FROM employees GROUP BY department

Let and const are block-scoped while var is function-scoped.

• let and const variables cannot be redeclared in the same scope

• let and var variables can be reassigned while const variables cannot

• var variables are hoisted to the top of their scope while let and const are not

• let and const variables are not accessible outside their block scope

Angular life cycle consists of several phases that a component goes through from creation to destruction.

• Angular components go through several life cycle hooks such as ngOnInit, ngOnChanges, ngOnDestroy, etc.

• ngOnInit is used for initialization logic, ngOnChanges is used for detecting changes in input properties, ngOnDestroy is used for cleanup tasks.

• Life cycle hooks allow developers to tap into key moments in a component's life cycle.

Debugging in production requires a systematic approach to identify and resolve the issue.

• Start by reproducing the issue in a test environment

• Check server logs and error messages for clues

• Use debugging tools like Chrome DevTools or Firebug

• Check network traffic and server response times

• Rollback recent changes if necessary

• Communicate with stakeholders and prioritize fixes

Use Boyer-Moore Majority Vote Algorithm to find element with count more than n/2.

• Initialize candidate element and count

• Iterate through array, updating count if same as candidate or decrementing if different

• If count becomes 0, update candidate element

• Iterate again to confirm candidate element count is more than n/2

Use JavaScript methods to extract desired output from a complex object

• Use Object.keys() to get an array of keys in the object

• Use Object.values() to get an array of values in the object

• Use Object.entries() to get an array of key-value pairs in the object

Closure is a function that has access to its own scope, as well as the scope in which it was defined.

• Closure allows a function to access variables from its outer scope even after the outer function has finished executing.

• It is created whenever a function is defined within another function.

• Example: function outerFunction() { let outerVar = 'I am outer'; function innerFunction() { console.log(outerVar); } return innerFunction; }

• Hoisting is a JavaScript mechanism where variable ...read more

Optimizing frontend code involves minimizing file sizes, reducing HTTP requests, using efficient algorithms, and implementing caching strategies.

• Minimize file sizes by removing unnecessary code, using minification tools, and optimizing images.

• Reduce HTTP requests by combining files, using sprites, and lazy loading resources.

• Use efficient algorithms and data structures to improve performance.

• Implement caching strategies such as browser caching, CDN caching, and server-side cac...read more

Implemented security measures such as HTTPS, input validation, and user authentication to protect websites from attacks.

• Implemented HTTPS to encrypt data transmission between the server and client

• Performed input validation to prevent SQL injection and cross-site scripting attacks

• Implemented user authentication to control access to sensitive information

• Regularly updated security patches and conducted security audits

A fetch and filter component for data retrieval and manipulation

• Use fetch API to retrieve data from an API endpoint

• Implement a filter function to manipulate the retrieved data based on user input

• Display the filtered data in the UI

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 within its scope.

• Let and Const are not hoisted like Var.

• Const must be initialized during declaration.

setTimeout executes a function once after a specified time, setInterval executes a function repeatedly at specified intervals, setImmediate executes a function immediately after the current event loop.

• setTimeout executes a function once after a specified delay.

• setInterval executes a function repeatedly at specified intervals.

• setImmediate executes a function immediately after the current event loop.

• Example: setTimeout(() => { console.log('Hello'); }, 1000);

• Example: setInterval...read more

Flex in CSS is a layout module that allows elements to align and distribute space within a container.

• Flexbox is used for creating flexible and responsive layouts.

• It allows for easy alignment and distribution of elements within a container.

• Flex properties include flex-direction, justify-content, align-items, and flex-grow.

Angular is a popular front-end framework for building dynamic web applications.

• Angular is developed and maintained by Google.

• It uses TypeScript for building applications.

• Angular provides features like two-way data binding, dependency injection, and routing.

• Components are the building blocks of Angular applications.

• Angular CLI is used for creating, building, and testing Angular projects.

Resolve a list of promises to get the output

• Use Promise.all() method to wait for all promises to resolve

• The output will be an array of resolved values in the same order as the input promises

• Handle any errors that may occur during promise resolution

NGRX is a state management library for Angular applications, inspired by Redux.

• NGRX helps manage the state of an Angular application in a predictable way

• It uses a unidirectional data flow and immutable state

• NGRX consists of actions, reducers, selectors, and effects

• Example: Actions define events that occur in the application, Reducers specify how the state changes in response to actions

Create a component to display concentric circles

• Use HTML canvas element to draw circles

• Calculate the radius and position of each circle

• Use CSS for styling and positioning if needed

Context API is a feature in React that allows sharing data between components without having to pass props manually.

• Create a context using createContext() method

• Use the Provider component to wrap the components that need access to the context

• Access the context data using the useContext() hook within the consuming components

const is used to declare a variable with a constant value, while object.freeze is used to make an object immutable.

• const is used to declare a variable with a constant value that cannot be reassigned

• object.freeze is used to make an object immutable, preventing any changes to its properties

• const can be used with primitive types and objects, while object.freeze is only applicable to objects

• const does not prevent changes to the properties of an object, while object.freeze does

Virtual DOM is a lightweight copy of the actual DOM that allows for efficient updates and rendering in web applications.

• Virtual DOM is a concept used in frameworks like React to improve performance by minimizing direct manipulation of the actual DOM.

• When changes are made to the virtual DOM, a comparison is done with the actual DOM to determine the minimal updates needed for rendering.

• This process helps reduce the number of DOM manipulations, leading to faster rendering and im...read more

box-sizing: border-box is a CSS property that includes padding and border in the element's total width and height.

• It changes the box model so that padding and border are included in the element's total width and height

• Helps in easier layout design as the total width and height of the element remains consistent

• Example: div { box-sizing: border-box; width: 100px; padding: 10px; border: 1px solid black; }

Semantic tags in HTML are specific tags that provide meaning and structure to the content, making it easier for search engines and screen readers to understand.

• Semantic tags help improve SEO by providing context to search engines.

• They also improve accessibility for screen readers by clearly defining the structure of the content.

• Examples of semantic tags include

  ,

Design Giphy with loader using the API

• Use Giphy API to fetch trending GIFs

• Implement a loader while fetching data

• Display the GIFs on the frontend

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.

A reference variable is a variable that stores the memory address of another variable.

• Reference variables are used to access the value of the variable they point to.

• They are commonly used in programming languages like C++ and Java.

• Example: int x = 10; int& ref = x; // ref now refers to the variable x

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.

I have received multiple job offers with varying compensation packages. I am looking for a competitive salary based on my experience and skills.

• I have received multiple job offers with different compensation packages

• I am looking for a competitive salary based on my experience and skills

• I am open to negotiation based on the offer and benefits provided