Limestone Digital Node Js Backend Developer Interview Questions and Answers

I have 5 years of experience working with Node.js in various projects and environments.

• 5 years of hands-on experience with Node.js

• Developed multiple backend applications using Node.js

• Familiar with popular Node.js frameworks like Express.js

• Experience in optimizing performance and scalability of Node.js applications

• Worked on integrating Node.js with databases like MongoDB and MySQL

Yes, I have experience with PostgreSQL.

• I have worked on multiple projects where PostgreSQL was used as the database.

• I am proficient in writing complex SQL queries and optimizing database performance.

• I have experience in setting up and maintaining PostgreSQL databases.

• I have used PostgreSQL in conjunction with Node.js for backend development.

Yes, I have experience with GraphQL.

• I have worked on implementing GraphQL APIs in various projects.

• I am familiar with creating schemas, resolvers, and queries in GraphQL.

• I have used tools like Apollo Server and GraphQL Playground for development.

A closure in Javascript is a function that has access to its own scope, as well as the outer function's scope.

• A closure allows a function to access variables from an outer function even after the outer function has finished executing.

• Closures are commonly used to create private variables and functions in Javascript.

• Example: function outerFunction() { let outerVar = 'I am outer'; return function innerFunction() { consol...read more

Event loop is a mechanism in Node.js that allows non-blocking I/O operations to be performed asynchronously.

• Event loop is responsible for handling asynchronous operations in Node.js.

• It allows Node.js to perform multiple operations concurrently without blocking the execution.

• Event loop continuously checks the event queue for new events and executes them in a non-blocking manner.

• Example: When a file is being read asynchr...read more

Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope during compilation.

• Variable declarations are hoisted to the top of their scope but not their initializations.

• Function declarations are fully hoisted, meaning they can be called before they are declared.

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

Event loop is a mechanism in Node.js that allows non-blocking I/O operations to be performed asynchronously.

• Event loop continuously checks the call stack for any functions that need to be executed.

• If the call stack is empty, event loop checks the callback queue for any pending tasks.

• Event loop moves tasks from the callback queue to the call stack for execution.

• This allows Node.js to handle multiple I/O operations concu...read more

Temporal dead zone is the period between entering scope and being able to access a variable.

• Occurs when trying to access a variable before it is declared

• Caused by hoisting in JavaScript

• Example: accessing a let or const variable before its declaration will result in a ReferenceError

let, const, and var are JavaScript keywords for variable declaration with different scopes and mutability rules.

• var is function-scoped or globally scoped, while let and const are block-scoped.

• let allows variable reassignment: let x = 10; x = 20;

• const creates a constant reference: const y = 30; y cannot be reassigned.

• var hoists the variable declaration, meaning it's accessible before its declaration: console.log(a); var...read more

A pipe in Node.js is a mechanism that allows you to connect the output of one stream to the input of another stream.

• Pipes are used to read data from a readable stream and write it to a writable stream.

• They are created using the pipe() method.

• Pipes help in simplifying the code by avoiding nested callbacks.

• Example: readableStream.pipe(writableStream);

Implement a custom event emitter class in Node.js

• Create a class MyEventEmitter with methods 'on' and 'emit'

• Store event listeners in an object with event names as keys and arrays of callbacks as values

• Implement 'on' method to add event listeners to the object

• Implement 'emit' method to trigger all callbacks for a given event