React
What is React?
React is a JavaScript library developed by Facebook used for building user interfaces, mainly for web applications. It allows us to create reusable UI components. I would use React because it helps in creating dynamic and interactive web pages efficiently. Its virtual DOM feature makes the app faster and improves performance. It's also widely used and supported by a large community.
What is SQL and why is it important?
SQL, which stands for Structured Query Language, is a programming language designed for managing and manipulating relational databases. It is important because it allows us to create, read, update, and delete (CRUD) data in a database, which is essential for data-driven decision making in businesses.
What is C# and why is it used?
C# is a modern, object-oriented programming language developed by Microsoft as part of the .NET initiative. It's widely used for developing Windows applications, web services, and server-side applications. C# is popular due to its simplicity, robustness, and versatility. It offers features like garbage collection, exception handling, and type safety, making it suitable for a wide range of programming tasks.
What is JSX and why does React use it?
JSX stands for JavaScript XML. It allows us to write HTML-like code inside JavaScript. It makes the code more readable and easier to understand. React uses JSX because it simplifies the process of creating UI components, and under the hood, it translates these elements into regular JavaScript objects.
Can you explain the difference between DELETE and TRUNCATE commands?
Both DELETE and TRUNCATE are used to remove data from a table. The main difference is that DELETE removes specific rows based on a condition and can be used with a WHERE clause, whereas TRUNCATE removes all rows from a table, resetting the table to its empty state. Also, DELETE operations can be rolled back if the database is in a transaction, but TRUNCATE operations cannot be rolled back in some SQL databases.
What are properties in C#?
Properties in C# are members that provide a flexible mechanism to read, write, or compute the values of private fields. Properties can be used as if they are public data members, but they are actually special methods called accessors. This encapsulation of data helps in data validation and better control over access.
How do you handle events in React?
In React, events are handled using functions. Unlike regular JavaScript, where we use lowercase for event names, in React, we use camelCase syntax. For example, onClick instead of onclick. We pass a function to the event handler rather than a string of code.
What are joins in SQL, and can you name and describe the different types?
Joins in SQL are used to combine rows from two or more tables based on a related column. The main types of joins are:
Can you explain inheritance in C#?
Inheritance is a fundamental concept of object-oriented programming and C# supports it. It allows a class (derived class) to inherit properties and methods from another class (base class). Inheritance promotes code reusability and establishes a relationship between different classes. In C#, a class can inherit from only one base class (single inheritance), but it can implement multiple interfaces.
What are hooks in React? Can you name a few?
Hooks are functions in React that let us use state and other React features in functional components. They're useful because before hooks, we could only use state in class components. Some basic hooks are useState, which lets us keep local state in a function component, and useEffect, which is for running side effects in function components.
What is a primary key, and how is it different from a foreign key?
A primary key is a unique identifier for each record in a database table, ensuring that no two rows have the same primary key. A foreign key, on the other hand, is a field (or collection of fields) in one table that uniquely identifies a row of another table. The primary key and foreign key relationship is used to maintain referential integrity between the tables.
What are delegates in C#, and why are they used?
A delegate in C# is a type that safely encapsulates a method, similar to a function pointer in other languages. Delegates are used to pass methods as arguments to other methods and can be used to define callback methods. They are essential for implementing event handling and lambda expressions. Delegates are particularly useful in designing extensible and flexible applications (like event-driven programs).
Can you explain the lifecycle of a React component?
In React, each component goes through several stages during its life. These are called lifecycle phases. There are three main phases:
How would you improve the performance of a SQL query?
To improve the performance of a SQL query, I would:
What is the difference between a class and an object in C#?
A class is a blueprint or a template for creating objects. It defines properties, methods, and events. An object, on the other hand, is an instance of a class. When a class is instantiated, memory is allocated for the object, and it's given a unique identity. The object encapsulates the data and behavior defined in the class.