Virtual Height IT Services Interview Questions, Process, and Tips

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.

Closures are functions that have access to their own scope, as well as the scope in which they were defined.

• Closures allow functions to access variables from their outer scope even after the outer function has finished executing.

• They are commonly used in event handlers, callbacks, and in functional programming.

• Example: const outerFunction = () => { const outerVar = 'I am outer'; return () => { console.log(outerVar); };...read more

JavaScript is a high-level, interpreted programming language used for creating interactive websites and web applications.

• JavaScript is often used for client-side scripting to make web pages interactive.

• It can also be used for server-side development with Node.js.

• JavaScript is versatile and can be used for creating games, mobile apps, and more.

Spread operator allows an iterable to be expanded in places where zero or more arguments or elements are expected. Rest operator collects all the remaining elements into an array.

• Spread operator is denoted by three dots (...) and is used to expand elements of an iterable like an array or object.

• Rest operator is also denoted by three dots (...) and is used to collect multiple elements into a single array.

• Spread operator...read more

Callback hell is a situation in asynchronous JavaScript programming where multiple nested callbacks make the code difficult to read and maintain.

• Occurs when multiple asynchronous operations are nested within each other

• Leads to deeply nested code structure which is hard to read and debug

• Can be avoided by using promises, async/await, or modularizing code

Asynchronous nature in Node JS refers to the ability of the program to execute multiple tasks simultaneously without blocking the main thread.

• Allows non-blocking I/O operations, improving performance and scalability

• Uses event-driven architecture to handle multiple requests concurrently

• Uses callbacks, promises, and async/await for handling asynchronous operations

Async await in Node.js is a feature that allows you to write asynchronous code in a synchronous manner.

• Async await is built on top of Promises in Node.js.

• It allows you to write asynchronous code that looks like synchronous code, making it easier to read and maintain.

• The 'async' keyword is used to define a function as asynchronous, while the 'await' keyword is used to wait for a Promise to resolve before continuing.

• Usin...read more