Perficient Interview Questions and Answers

Promises are used in JavaScript to handle asynchronous operations and avoid callback hell.

• Promises are used to handle asynchronous operations in a more readable and manageable way.

• They help avoid callback hell by chaining multiple asynchronous operations together.

• Promises can be in one of three states: pending, fulfilled, or rejected.

• They allow for better error handling with the use of .catch() method.

• Promises can...read more

Object-oriented programming paradigm that focuses on objects and classes

• Encapsulation: bundling data and methods that operate on the data into a single unit

• Inheritance: ability of a class to inherit properties and behavior from another class

• Polymorphism: ability to present the same interface for different data types

Enum is a data type in programming that consists of a set of named constants.

• Enums are used to define a set of named constants, making the code more readable and maintainable.

• Enums can be used to represent a fixed number of possible values for a variable.

• Enums can also be used to improve type safety by restricting the possible values that a variable can hold.

• Example: enum Color { RED, GREEN, BLUE }

Rank assigns unique numbers to rows based on order of values, while dense rank assigns consecutive numbers without gaps.

• Rank leaves gaps in ranking sequence if there are ties, while dense rank does not

• Rank assigns the same rank to tied values, while dense rank assigns consecutive ranks

• Example: Rank - 1, 2, 3, 4, 4, 6; Dense Rank - 1, 2, 3, 4, 4, 5

Joins are used in SQL to combine rows from two or more tables based on a related column between them.

• Inner Join: Returns rows when there is at least one match in both tables.

• Left Join (or Left Outer Join): Returns all rows from the left table and the matched rows from the right table.

• Right Join (or Right Outer Join): Returns all rows from the right table and the matched rows from the left table.

• Full Join (or Full ...read more

Payment gateway implementation involves integrating a secure platform for processing online transactions.

• Choose a payment gateway provider based on your business needs and requirements

• Obtain API credentials from the chosen provider

• Integrate the payment gateway API into your website or application

• Test the payment gateway integration thoroughly to ensure it functions correctly

• Ensure compliance with security standard...read more

Tools used for data engineering include ETL tools, programming languages, databases, and cloud platforms.

• ETL tools like Apache NiFi, Talend, and Informatica are used for data extraction, transformation, and loading.

• Programming languages like Python, Java, and Scala are used for data processing and analysis.

• Databases like MySQL, PostgreSQL, and MongoDB are used for storing and managing data.

• Cloud platforms like AWS...read more