20+ Senior Frontend Software Engineer Interview Questions and Answers

Designing an online card game using pure JavaScript involves creating game logic, UI, and event handling without frameworks.

• Define the game rules and mechanics, such as how many players, card distribution, and win conditions.

• Create a basic HTML structure for the game interface, including elements for the deck, player hands, and game status.

• Use JavaScript to manage game state, such as shuffling cards, dealing them to players, and tracking scores.

• Implement event listeners for u...read more

Enhancing Facebook's news feed performance involves techniques like tree shaking, caching, and optimizing rendering.

• Implement tree shaking to eliminate unused code, reducing bundle size and improving load times.

• Utilize caching strategies, such as service workers, to store frequently accessed data and reduce server requests.

• Optimize images and media using formats like WebP for faster loading and reduced bandwidth usage.

• Employ lazy loading for images and components to defer loa...read more

Optimizing a solution involves improving efficiency, reducing complexity, and enhancing performance in code execution.

• Analyze time complexity: Use Big O notation to evaluate performance.

• Reduce unnecessary computations: Cache results of expensive function calls.

• Use efficient data structures: For example, prefer HashMaps for quick lookups.

• Minimize DOM manipulations: Batch updates to the DOM to reduce reflows.

• Leverage asynchronous programming: Use Promises or async/await to hand...read more

Memoization is a technique to optimize function calls by caching their results.

• Memoization is used to store the results of expensive function calls and return the cached result when the same inputs occur again.

• It improves performance by avoiding redundant computations.

• Fibonacci sequence is a classic example to demonstrate memoization.

• Memoization can be implemented using an object or an array to store the cached results.

Program to check duplicate numbers in a phone number

• Convert phone number to an array of strings

• Loop through the array and check for duplicates

• Use a hash table to keep track of numbers already seen

Seeking new challenges and growth opportunities in a different environment.

• Looking for new challenges and opportunities to grow professionally

• Interested in working with new technologies and tools

• Seeking a more collaborative team environment

• Want to expand my skill set and knowledge in frontend development

Find the length of the longest substring without repeating characters.

• Use a sliding window approach to keep track of the longest substring without repeating characters.

• Use a hashmap to store the index of each character as you iterate through the string.

• Update the start index of the window when a repeating character is encountered.

Search and Sort algorithms are essential for efficient data manipulation in frontend development.

• Search algorithm like binary search can be implemented to quickly find elements in a sorted array.

• Sort algorithms like bubble sort or quicksort can be used to arrange elements in a specific order.

• Implementing these algorithms in JavaScript involves writing functions that iterate through arrays and compare elements.

Create Microsoft Teams call UI using HTML and CSS.

• Use HTML to structure the layout of the call UI

• Use CSS to style the elements such as buttons, video feeds, and chat box

• Implement responsive design for different screen sizes

• Include features like mute/unmute, video on/off, screen sharing, and chat functionality

Design a library to log drop-rate in form fields.

• Create a function to track changes in form fields

• Implement a mechanism to calculate drop-rate based on user interactions

• Store drop-rate data in a database for analysis

Destructuring in JavaScript allows unpacking values from arrays or properties from objects into distinct variables.

• Array Destructuring: const arr = [1, 2, 3]; const [a, b] = arr; // a = 1, b = 2

• Object Destructuring: const obj = { x: 10, y: 20 }; const { x, y } = obj; // x = 10, y = 20

• Default Values: const arr = [1]; const [a, b = 2] = arr; // a = 1, b = 2

• Nested Destructuring: const obj = { a: { b: 2 } }; const { a: { b } } = obj; // b = 2

• Rest Operator: const arr = [1, 2, 3, 4...read more

Evaluate infix expressions by converting them to postfix and calculating the result using a stack.

• Infix expressions are standard mathematical expressions (e.g., A + B).

• To evaluate, convert infix to postfix using the Shunting Yard algorithm.

• Use a stack to evaluate the postfix expression.

• Example: Infix: (3 + 4) * 5 converts to Postfix: 3 4 + 5 *.

• Evaluate Postfix: Push 3, push 4, pop 3 and 4, add to get 7, push 5, multiply to get 35.

Clear and clear both CSS properties manage element visibility and layout in web design.

• The 'clear' property prevents elements from floating beside each other. Example: 'clear: both;' ensures no floated elements are adjacent.

• The 'clear' property can take values like 'left', 'right', and 'both', controlling the flow of elements around floated items.

• Using 'clear: left;' will push an element below any floated elements on the left side.

• The 'clear' property is often used in layouts...read more

PUB SUB pattern is a messaging pattern where senders of messages (publishers) do not program the messages to be sent directly to specific receivers (subscribers).

• Publishers send messages without knowing who the subscribers are

• Subscribers receive messages without knowing who the publishers are

• Commonly used in event-driven systems to decouple components

Vendor prefixes are used in CSS to add experimental features that are not yet standardized.

• Vendor prefixes are added to CSS properties to support experimental features.

• They are used to test new features before they are standardized.

• Examples of vendor prefixes include -webkit-, -moz-, -ms-, and -o-.

• Vendor prefixes should be used sparingly and with caution, as they can cause compatibility issues.

• It is important to include the standard version of the property after the vendor-pr...read more

Promise.all executes multiple promises in parallel and resolves when all are fulfilled or rejects if any promise fails.

• Takes an array of promises as input.

• Returns a single promise that resolves when all input promises resolve.

• If any promise rejects, the returned promise rejects with that reason.

• Example: Promise.all([Promise.resolve(1), Promise.resolve(2)]) resolves to [1, 2].

• Example: Promise.all([Promise.resolve(1), Promise.reject('error')]) rejects with 'error'.

Long polling waits for server response before sending new request, short polling sends requests at regular intervals.

• Long polling is more efficient for real-time updates

• Short polling is simpler to implement but less efficient

• Long polling reduces server load by minimizing requests

• Short polling can lead to higher network traffic

• Example: Chat applications often use long polling for instant messaging