Cotelligent Interview Questions and Answers

let, var, and const are all used to declare variables in JavaScript, but they have different scopes and mutability.

• let: block-scoped, can be reassigned

• var: function-scoped, can be reassigned

• const: block-scoped, cannot be reassigned, but its properties can be modified

Struct is a value type while object is a reference type in C#.

• Structs are value types and stored on stack, while objects are reference types and stored on heap.

• Structs are passed by value, while objects are passed by reference.

• Structs do not support inheritance, while objects do.

• Example: struct Point { int x, y; } vs class Point { int x, y; }

Polymorphism is the ability of a function or method to behave differently based on the object it is called with.

• Polymorphism allows objects of different classes to be treated as objects of a common superclass.

• It enables a single interface to be used for different data types.

• Examples include method overloading and method overriding in object-oriented programming.

Compiler programming languages convert source code into machine code before execution, while interpreter programming languages execute code line by line.

• Compiler programming languages: C, C++, Java

• Interpreter programming languages: Python, Ruby, JavaScript

A promise is an object representing the eventual completion or failure of an asynchronous operation.

• Promises are used in JavaScript to handle asynchronous operations.

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

• Promises can be chained using .then() to handle success and failure callbacks.

• Example: Fetching data from an API returns a promise that resolves with the data or rejects with an error.

Hoisting is a JavaScript mechanism where variable and function declarations are moved to the top of their containing scope during compilation.

• Variable and function declarations are hoisted to the top of their scope.

• Only declarations are hoisted, not initializations.

• Function declarations take precedence over variable declarations.

Event loop is a mechanism in programming that allows for asynchronous execution of code by continuously checking for and handling events.

• Event loop is commonly used in JavaScript to handle asynchronous operations like setTimeout, setInterval, and AJAX requests.

• It allows for non-blocking I/O operations, ensuring that the program can continue running while waiting for I/O operations to complete.

• Event loop works by contin...read more

Calculate the frequency of a specific integer in an array of strings.

• Iterate through the array and use a hashmap to store the frequency of each integer.

• Return the frequency of the specified integer from the hashmap.

Node.js is a runtime environment that allows you to run JavaScript on the server side.

• Node.js is built on Chrome's V8 JavaScript engine.

• It uses an event-driven, non-blocking I/O model.

• Node.js is commonly used for building server-side applications and APIs.

• It has a large ecosystem of libraries and frameworks, such as Express and Socket.io.

DNS port number is 53.

• DNS port number is used for DNS queries and responses.

• It is a well-known port number, which is 53.

• DNS uses both TCP and UDP protocols on port 53.

SSH port number is 22.

• SSH port number is used for secure communication over a network.

• Default port number for SSH is 22.

• Port number can be changed for security reasons.

• Example: ssh user@hostname -p 2222

A brute force attack is a trial-and-error method used by hackers to crack passwords or encryption by systematically trying all possible combinations.

• Brute force attacks are time-consuming but effective against weak passwords.

• Hackers use automated tools to try all possible combinations until the correct one is found.

• Examples include trying all possible 4-digit PIN codes or dictionary words as passwords.

• Strong passwords ...read more