EBA SOLUTIONS Full Stack Developer Interview Questions and Answers

Closure is a feature in programming languages that allows a function to access variables from its outer scope even after it has finished executing.

• Closure is created when a nested function references variables from its parent function.

• It allows for data encapsulation and privacy in JavaScript.

• Closures are commonly used in event handlers, callbacks, and asynchronous programming.

• They can be used to create private variabl...read more

JS hoisting is a mechanism where variable and function declarations are moved to the top of their scope during compilation.

• Variable declarations are hoisted but not their initializations.

• Function declarations are fully hoisted, including their definitions.

• Hoisting can lead to unexpected behavior if not understood properly.

• Example: console.log(x); var x = 5; // Output: undefined

CSS position properties determine how an element is positioned on a web page.

• static: default position, elements flow in document order

• relative: positioned relative to its normal position

• absolute: positioned relative to its nearest positioned ancestor

• fixed: positioned relative to the browser window

• sticky: positioned based on scroll position

React has several component lifecycles, including mounting, updating, and unmounting.

• Mounting: when a component is being created and inserted into the DOM

• Updating: when a component is being re-rendered due to changes in props or state

• Unmounting: when a component is being removed from the DOM

Ref is used in React to access and manipulate the DOM directly.

• Ref provides a way to access and modify DOM elements or React components.

• It is commonly used for focusing input fields, triggering animations, or integrating with third-party libraries.

• Ref can be created using the useRef() hook or by using the ref attribute in class components.

• Example: const inputRef = useRef();

• Example: const button

Designing the database for Slack

• Create tables for users, channels, messages, and teams

• Use foreign keys to establish relationships between tables

• Include columns for user details, channel details, message content, and timestamps

• Consider indexing frequently queried columns for performance optimization

To improve db performance, optimize queries, use indexing, cache data, and scale horizontally.

• Optimize queries by using appropriate indexes and avoiding unnecessary joins

• Cache frequently accessed data to reduce database load

• Scale horizontally by distributing the database across multiple servers

• Use database monitoring tools to identify and resolve performance bottlenecks

CDN stands for Content Delivery Network. It is a distributed network of servers that helps deliver web content efficiently.

• CDN improves website performance by caching content closer to the user

• It reduces latency and improves page load times

• CDN helps handle high traffic loads and prevents server overload

• It provides global coverage and ensures content availability worldwide

• CDN can deliver various types of content like im...read more

To improve API latency, optimize database queries, use caching, implement load balancing, and optimize code.

• Optimize database queries by using indexes, reducing unnecessary joins, and optimizing query execution plans.

• Implement caching to store frequently accessed data in memory, reducing the need for repeated database queries.

• Use load balancing to distribute incoming requests across multiple servers, preventing any sin...read more