Treez Interview Questions and Answers

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

• Promises are used to handle asynchronous operations in JavaScript.

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

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

• Example: new Promise((resolve, reject) => { ... }).then(result => { ... }).catch(error => { ... });

Callback is a function passed as an argument to another function to be executed later. Async await is a syntax for writing asynchronous code in a synchronous manner.

• Callback is used in event handling, asynchronous programming, and more.

• Async await is a modern way to write asynchronous code in a synchronous style.

• Example: Callback - setTimeout function in JavaScript.

• Example: Async await - fetching data from an API in Ja

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

• 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.

• Example: console.log(x); var x = 5; // Output: undefined

Event loop is a mechanism in programming that allows for asynchronous execution of code.

• Event loop is commonly used in JavaScript to handle asynchronous operations.

• It allows for non-blocking I/O operations by continuously checking the event queue.

• Event loop ensures that the program does not get stuck waiting for a single operation to complete.

EventEmitter is a class in Node.js that allows multiple functions to be attached to an event and triggered when the event is emitted.

• EventEmitter is a core module in Node.js that allows communication between objects in a loosely coupled way.

• It is used for handling events in Node.js applications.

• Listeners can be attached to EventEmitter instances using the 'on' method and events can be emitted using the 'emit' method.

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Request and Response objects are created in Node.js using the 'http' module.

• Require the 'http' module in your code

• Use the 'http.createServer()' method to create a server

• Access the request and response objects in the callback function

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

• let: block-scoped variable, can be reassigned

• var: function-scoped variable, can be reassigned

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

No, you cannot declare a variable with the same name using var keyword.

• Variables declared with var keyword can only be declared once within the same scope

• Attempting to declare a variable with the same name using var will result in a syntax error

Middleware is software that acts as a bridge between different applications or components, allowing them to communicate and work together.

• Middleware facilitates communication between different software components

• It can handle tasks such as data conversion, security, and logging

• Examples include message brokers like RabbitMQ, web servers like Apache Tomcat, and API gateways like Kong

Debugging memory leaks involves identifying the source of the leak and fixing it to free up memory.

• Use memory profiling tools like Valgrind or Instruments to detect memory leaks

• Check for unreleased memory allocations in the code

• Look for circular references or retain cycles in object-oriented programming languages

• Use tools like LeakSanitizer in C/C++ programs to detect memory leaks

• Review code for potential memory leaks,