10+ ROITech Consulting Pvt Ltd. Interview Questions and Answers

Indexes in MongoDB improve query performance by allowing the database to quickly locate and retrieve specific documents.

• Indexes help to speed up query performance by allowing the database to quickly locate specific documents based on the indexed fields.

• Without indexes, MongoDB would have to perform a collection scan, which can be slow and resource-intensive.

• Indexes can be created on single fields or compound fields to further optimize query performance.

• However, indexes come w...read more

The JAVA API is a collection of pre-written classes and interfaces that provide ready-to-use functionality for Java developers.

• The JAVA API allows developers to save time and effort by using pre-built code for common tasks.

• It provides a wide range of classes and interfaces for various purposes such as file handling, networking, database connectivity, GUI development, etc.

• Developers can leverage the API to access system resources, interact with external services, and perform c...read more

Modules in Node.js are reusable blocks of code that encapsulate related functionality.

• Modules in Node.js can be built-in modules like fs (file system) or third-party modules like express.

• Modules help in organizing code into separate files for better maintainability and reusability.

• Modules can be imported using the require() function in Node.js.

Inheritance allows a class to inherit properties and behaviors from another class. Abstract classes cannot be instantiated and can have abstract methods. Interfaces define a contract for classes to implement.

• Inheritance allows a class to inherit properties and behaviors from another class

• Abstract classes cannot be instantiated and can have abstract methods

• Interfaces define a contract for classes to implement

Yes, let and const variables are hoisted but not initialized.

• let and const variables are hoisted to the top of their block scope, but they are not initialized until the actual line of code is executed.

• This means that you cannot access a let or const variable before it is declared in the code.

• For example, trying to access a let variable before it is declared will result in a ReferenceError.

Mongoose is an Object Data Modeling (ODM) library for MongoDB that provides a higher level of abstraction and simplifies interactions with the database.

• Mongoose provides schema validation which helps maintain data integrity.

• Mongoose simplifies querying and data manipulation with built-in functions.

• Mongoose supports middleware functions for pre and post processing of data operations.

Hooks are a feature in React that allow you to use state and other React features in functional components. useRef is a hook that allows you to create a mutable object that persists for the lifetime of the component.

• Hooks are used to add state and lifecycle methods to functional components in React

• useRef is used to create a mutable reference that persists between renders

• useRef can be used to access DOM elements directly in functional components

ES6 introduced several new features and improvements to JavaScript, making it more powerful and efficient.

• Arrow functions for more concise syntax

• Let and const for block-scoped variables

• Classes for easier object-oriented programming

• Template literals for easier string interpolation

• Default parameters and rest parameters for function arguments

• Destructuring assignment for easier data extraction

• Promises for asynchronous programming

• Modules for better code organization

Global context refers to the overall environment or setting in which something exists or operates.

• Global context encompasses all variables, functions, and objects that are accessible throughout an entire program.

• It can be thought of as the 'big picture' view of a program's execution.

• In web development, global context includes the window object in JavaScript.

Temporal dead zone is a period during the variable creation process where accessing the variable results in a ReferenceError.

• Occurs when trying to access a variable before it has been declared with let or const

• Happens due to the variable being in the temporal dead zone until it is declared

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

Throws is used for checked exceptions in Java, while throw is used to explicitly throw an exception.

• Throws is used in method signature to declare that the method may throw a checked exception.

• Throw is used to actually throw an exception in the code.

• Example: public void method() throws IOException { //code }

• Example: throw new IOException();

Program to find sum and average of digits in a string, ignoring other characters.

• Iterate through each character in the string and check if it is a digit.

• If it is a digit, convert it to an integer and add it to the sum.

• Keep track of the count of digits to calculate the average at the end.

Ethernet cable is commonly used to transfer data in networking applications.

• Ethernet cable is commonly used for wired internet connections

• USB cable is used for transferring data between devices like computers and smartphones

• HDMI cable is used for transferring audio and video data between devices like TVs and laptops

Find the second most occurrence of a string in an array of strings in JavaScript.

• Create a map to store the count of each string in the array

• Sort the map by values in descending order to find the most occurrence

• Return the key of the second element in the sorted map

Create a todo app with react and basic form validation

• Use React to create components for adding, displaying, and deleting todos

• Implement basic form validation using state and event handlers

• Utilize CSS for styling the app and make it user-friendly

Used a microservices architecture with React as the front-end framework.

• Implemented separate services for different functionalities like user authentication, data retrieval, and payment processing.

• Used RESTful APIs to communicate between services.

• Utilized Redux for state management and to maintain a single source of truth for the application.

• Deployed the application on AWS using Docker containers for scalability and flexibility.

Find the second most occurrence of string in an array of strings.

• Create a dictionary to store the count of each string in the array

• Sort the dictionary by count in descending order

• Return the key of the second element in the sorted dictionary

Embedded development is the process of creating software that is embedded into hardware devices to control their functions.

• Involves programming microcontrollers or microprocessors

• Requires knowledge of hardware and software interactions

• Common in devices like smartphones, IoT devices, and automotive systems