OneDirect (India) Senior Software Engineer 2 Interview Questions and Answers

Q1. Rate yourself in js, node js, react, MongoDB (separately)
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Q2. Typeof null, typeof undefined, typeof {}, typeof NaN
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Q3. What changes came in es6
Ans. 
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 prog
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Q4. This keyword, closures, hoisting
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Q5. Are let and cont variables hoisted?
Ans. 
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.
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Q6. What is global context
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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.
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Q7. What is temporal deadzone
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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
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Q8. What is modules? types of modules in nodejs
Ans. 
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.
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Q9. Index in mongodb, why we need index, is index good or bad?
Ans. 
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 ...read more
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Q10. What are hooks , use of useRef
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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 directl
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Q11. Fs module, http module, worker thread?
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Q12. Why we use mongoose not mongodb driver?
Ans. 
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.
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Aptitude questions with some basic coding questions

They have given 3 coding questions and some pseudo codings

Q1. Tell about your self
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Q2. Some coding questions
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Based on JavaScript and Java.

A task based on JavaScript.

Basic aptitude questions were asked of easy level.

Q1. Dbms , oops , C++ , sql , aws , powerpoint
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Q1. Peak element in array
Ans. 
A peak element in an array is an element that is greater than or equal to its neighbors.
• Iterate through the array and check if the current element is greater than its neighbors.

• If the element at index i is greater than or equal to elements at indices i-1 and i+1, it is a peak element.

• Example: ['1', '3', '2', '4', '1'] has peak elements at index 1 and 3.
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Q2. 2 dimentional array rotate 90 degree
Ans. 
Rotate a 2D array by 90 degrees clockwise
• Transpose the array

• Reverse each row of the transposed array
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Pollitices current generation

Aptitude questions were easy and basics

Q1. They asked about projects, SQL basics, oops concepts and about java concepts
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Q2. It was an easy and average interview
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Aptitude test was quite easy; it had normal intelligence questions as well as some math

The coding test consisted of 2 medium HackerRank questions in any language

Q1. I had a face-to-face virtual interview. The interview round went for 45 minutes. They asked all sort of questions, from JAVA to SQL to basic Python. Also, DSA questions were asked.
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Q2. Difference between Truncate, Delete and Drop
Ans. 
Truncate removes all rows from a table, Delete removes specific rows, and Drop deletes the entire table structure.
• Truncate is a DDL command that removes all rows from a table but keeps the table structure intact.

• Delete is a DML command that removes specific rows based on a condition.

• Drop is a DDL command that deletes the entire table structure along with all its data.

• Truncate is faster than Delete as it does not log in...read more
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Q3. Difference between Sets, Lists, Tuples
Ans. 
Sets, Lists, and Tuples are all data structures in Python with different characteristics and use cases.
• Sets are unordered collections of unique elements. Example: {1, 2, 3}

• Lists are ordered collections of elements that can be modified. Example: [1, 2, 3]

• Tuples are ordered collections of elements that cannot be modified. Example: (1, 2, 3)
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Q1. Round 4 was another face-to-face interview with a senior.
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Array questions - sum the closest two element of array untill its one element