WITS Innovation Lab Node JS Developer Interview Questions and Answers

It is easy to solve the Aptitude question and some identifying outputs of program.

Q1. What is class?and write a logic for object in a class.
Ans. 
A class is a blueprint for creating objects in object-oriented programming.
• A class defines the properties and behaviors of objects.

• An object is an instance of a class.

• Example: Class 'Car' can have properties like 'color' and 'model', and behaviors like 'drive' and 'stop'.
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Q2. 1.swap two numbers without using temp variable 2.Reverse the string.
Ans. 
Swap two numbers without using temp variable and reverse a string without using built-in functions.
• To swap two numbers without using temp variable, use bitwise XOR operation.

• To reverse a string without using built-in functions, use two pointers approach.

• Example for swapping numbers: a = a ^ b; b = a ^ b; a = a ^ b;

• Example for reversing a string: use two pointers to swap characters from start and end of the string.
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Now, I am preparing for the third round.
So, I don't know the Coding Question.

Q1. What are oops concepts in java, explain real time scenario
Ans. 
OOPs concepts in Java include inheritance, polymorphism, encapsulation, and abstraction.
• Inheritance allows a subclass to inherit properties and methods from a superclass.

• Polymorphism allows objects to take on multiple forms and behave differently based on their context.

• Encapsulation hides the implementation details of an object and only exposes necessary information.

• Abstraction allows for the creation of abstract class...read more
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Q2. Uses of interface, inheritance
Ans. 
Interfaces define contracts for behavior, while inheritance allows for code reuse and polymorphism.
• Interfaces allow for loose coupling and abstraction, enabling multiple implementations of the same behavior.

• Inheritance allows for code reuse and extension of existing classes, reducing code duplication.

• Polymorphism allows objects of different classes to be treated as if they were of the same class, simplifying code and i
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Q3. SQL query for join of tables
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SQL query for joining tables
• Use JOIN keyword to combine two or more tables based on a related column

• Specify the columns to be selected using SELECT keyword

• Use ON keyword to specify the condition for joining the tables

• Different types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN
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Q4. Java concepts used in your project
Ans. 
Used Java concepts such as inheritance, polymorphism, and exception handling in my project.
• Implemented inheritance to create a base class and derived classes with specific functionalities.

• Utilized polymorphism to allow objects of different classes to be treated as if they were of the same class.

• Implemented exception handling to handle errors and prevent program crashes.

• Used interfaces to define a set of methods that a ...read more
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Q5. Overloading vs overriding, practical uses
Ans. 
Overloading is having multiple methods with the same name but different parameters. Overriding is having a method in a subclass with the same name and parameters as a method in the superclass.
• Overloading is used to provide different ways to call a method with different parameters

• Overriding is used to provide a specific implementation of a method in a subclass

• Overloading is resolved at compile-time while overriding is r...read more
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Logical thinking and quantitative

One Java and one SQL and one js question

Q1. What is collections
Ans. 
Collections are data structures that store and organize multiple elements in a single unit.
• Collections provide methods to add, remove, and manipulate elements.

• Examples of collections include arrays, lists, sets, and maps.

• Collections can be used to efficiently manage and access large amounts of data.
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Q2. What is constructor
Ans. 
A constructor is a special method in a class that is automatically called when an object of that class is created.
• Constructors have the same name as the class they belong to

• They are used to initialize the object's state

• Constructors can have parameters to customize the initialization process
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Q3. What is data science
Ans. 
Data science is a field that uses scientific methods, algorithms, and systems to extract knowledge and insights from structured and unstructured data.
• Data science involves collecting, analyzing, and interpreting large amounts of data to make informed decisions.

• It combines statistics, machine learning, and domain knowledge to uncover patterns and trends in data.

• Data scientists use programming languages like Python and R...read more
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Q1. What is interface ?
Ans. 
An interface in software development defines a contract for classes to implement, specifying methods and properties.
• Interfaces in programming languages like Java and C# allow for multiple inheritance by defining a set of methods that a class must implement.

• Interfaces provide a way to achieve abstraction and polymorphism in object-oriented programming.

• Interfaces are used to define common behavior that multiple classes c...read more
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Q2. Hat is encapsulation
Ans. 
Encapsulation is the concept of bundling data and methods that operate on the data into a single unit.
• Encapsulation helps in hiding the internal state of an object and restricting access to it.

• It allows for better control over the data by preventing direct access from outside the class.

• Encapsulation promotes code reusability and makes the code easier to maintain.

• Example: In a class representing a car, the variables lik...read more
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10 apti questions and 10 technical mcq on cpp

Q1. Oops concept question
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Q2. Sql queries on join
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