Loumus Data Systems Interview Questions and Answers

let, var and const are all used to declare variables in JavaScript, but they differ in their scope and mutability.

• let has block scope and can be reassigned

• var has function scope and can be reassigned

• const has block scope and cannot be reassigned, but its properties can be mutated

Higher order functions are functions that take other functions as arguments or return functions as their output.

• Higher order functions can be used to create more flexible and reusable code.

• They allow for functions to be composed and combined in various ways.

• Examples of higher order functions include map, filter, and reduce in JavaScript.

• Higher order functions can also be used for currying and partial application.

A calculator app built using React

• Create a component for the calculator

• Use state to keep track of the input and result

• Implement functions for basic arithmetic operations

• Add buttons for each number and operation

• Display the input and result on the screen

Design a database schema for nested comments on a post

• Create a table for posts with a unique ID

• Create a table for comments with a unique ID, post ID, and parent comment ID

• Use foreign keys to link comments to posts and parent comments

• Use a recursive function to retrieve nested comments

Event loop is a mechanism in JavaScript that handles asynchronous operations.

• Event loop continuously checks the call stack and the task queue.

• If the call stack is empty, it takes the first task from the queue and pushes it to the call stack.

• Event loop is responsible for handling callbacks and promises.

• Event loop prevents blocking of the main thread.