o9 Solutions Senior Software Engineer Interview Questions and Answers

Q1. What are closures
Ans. 
Closures are functions that have access to variables from their containing scope even after the scope has closed.
• Closures allow functions to access variables from their outer function even after the outer function has finished executing.

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

• Closures help in maintaining state in functional programming.
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Q2. What is virtual DOM
Ans. 
Virtual DOM is a lightweight copy of the actual DOM used for efficient updates in web development.
• Virtual DOM is a concept used in frameworks like React to improve performance by minimizing actual DOM manipulations.

• When changes are made to the virtual DOM, a comparison is done with the actual DOM to determine the minimal updates needed.

• This approach reduces the number of costly DOM operations, resulting in faster rende
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Q3. What are the data types in JS
Ans. 
Data types in JavaScript include number, string, boolean, object, function, undefined, and null.
• Number - represents numeric data, e.g. 10, 3.14

• String - represents textual data, e.g. 'hello', '123'

• Boolean - represents true or false values, e.g. true, false

• Object - represents complex data structures, e.g. { key: 'value' }

• Function - represents executable code, e.g. function() { }

• Undefined - represents a variable that has ...read more
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Q1. Write react code for counter
Ans. 
React code for a simple counter
• Create a functional component for the counter

• Use useState hook to manage the count state

• Render the count value and buttons to increment and decrement the count
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Q1. Salary discussion
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Q1. What are the OOPS concepts
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Q2. MultiThreading, synchronization
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Q1. Tell me about yourself
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Q1. Basic JS related question
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Q2. Angular Basic + Advance Question
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Aptitude test with aptitude based questions

Q1. What is variable hoisting.
Ans. 
Variable hoisting is a behavior in JavaScript where variable declarations are moved to the top of their scope during compilation.
• Variable declarations are hoisted to the top of their function or global scope.

• Only the declarations are hoisted, not the initializations.

• This can lead to unexpected behavior if variables are accessed before they are declared.
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Q2. What is closures in js
Ans. 
Closures in JavaScript allow functions to access variables from an outer function even after the outer function has finished executing.
• Closures are created whenever a function is defined within another function.

• Inner functions have access to the outer function's variables even after the outer function has returned.

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

• Example: function outer...read more
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Q1. How do you read an external text file
Ans. 
To read an external text file, you can use file handling techniques in programming languages like Python or Java.
• Use file handling functions like open(), read(), and close() in Python to read an external text file.

• In Java, use classes like FileReader and BufferedReader to read text files.

• Specify the file path and mode (read mode) when opening the file.

• Read the contents of the file line by line or as a whole, depending ...read more
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Q2. Write a java program to find the occurrences of characters
Ans. 
Java program to find occurrences of characters in a string
• Create a HashMap to store characters and their counts

• Iterate through the string and update the counts in the HashMap

• Print the characters and their counts from the HashMap
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Coding test was on Java programs. Basically for loop programs.

Normal aptitude questions.

Q1. Technical questions related to basics of languages and OOPS concepts.
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Q1. Normal HR questions nothing specific.
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Q1. Testing questions
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