Quantorix Technology Interview Questions and Answers

Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine that allows developers to run JavaScript on the server side.

• Node.js is used for building scalable network applications.

• It uses an event-driven, non-blocking I/O model that makes it lightweight and efficient.

• Node.js is commonly used for building web servers, APIs, and real-time applications.

• Example: Creating a simple web server using Node.js:

var is function scoped, let is block scoped, const is block scoped and cannot be reassigned.

• var is function scoped, let is block scoped, const is block scoped and cannot be reassigned

• var can be redeclared and updated, let can be updated but not redeclared, const cannot be redeclared or updated

• Example: var x = 10; let y = 20; const z = 30;

Hoisting is a JavaScript mechanism 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.

• Function declarations are hoisted before variable declarations.

• Only declarations are hoisted, not initializations.

Closure is the combination of a function bundled together with references to its surrounding state.

• Closure allows a function to access variables from its outer scope even after the outer function has finished executing.

• It helps in maintaining state in asynchronous operations.

• Example: function outerFunction() { let outerVar = 'I am outer'; return function innerFunction() { console.log(outerVar); }; }

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

• Middleware helps in integrating different systems and applications together.

• It provides a layer of abstraction for communication between components.

• Examples of middleware include web servers, message brokers, and API gateways.

MVC is a software design pattern that separates an application into three main components: Model, View, and Controller.

• Model represents the data and business logic of the application

• View is responsible for displaying the data to the user

• Controller acts as an intermediary between Model and View, handling user input and updating the Model accordingly