Happiest Minds Technologies Senior Software Engineer Interview Questions and Answers

The number of columns that can be created in a table depends on the database management system being used.

• The limit varies depending on the DBMS

• For MySQL, the limit is 4096 columns per table

• For Oracle, the limit is 1000 columns per table

• The number of columns can also be limited by the available memory and disk space

Design patterns are reusable solutions to common software problems. One example is the Singleton pattern.

• Creational patterns: Singleton, Factory, Abstract Factory, Builder

• Structural patterns: Adapter, Bridge, Composite, Decorator, Facade, Flyweight, Proxy

• Behavioral patterns: Chain of Responsibility, Command, Interpreter, Iterator, Mediator, Memento, Observer, State, Strategy, Template Method, Visitor

• Singleton pattern ensures a class has only one instance, and provides a globa...read more

OOPs concepts are the fundamental principles of object-oriented programming.

• Encapsulation - binding data and functions together

• Inheritance - creating new classes from existing ones

• Polymorphism - ability of objects to take on multiple forms

• Abstraction - hiding implementation details from users

Master database is the primary database that stores all the important data of an organization.

• Master database is the central repository of all the important data of an organization

• It is used to store and manage critical data such as customer information, financial data, and employee records

• It is usually the most secure and highly available database in an organization

• Examples of master databases include Oracle, SQL Server, and MySQL

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 not been assigned a value

• Null - represents an intentional ...read more

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.

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 rendering and improved user experience.