Siemens Energy Control System Engineer Interview Questions and Answers

Node.js is a runtime environment that allows you to run JavaScript code outside of a web browser.

• 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.

• It has a large ecosystem of open-source libraries and frameworks like Express.js.

Event loop is a mechanism that allows a program to efficiently handle multiple events or tasks concurrently.

• Event loop is commonly used in asynchronous programming to manage tasks that may take varying amounts of time to complete.

• It continuously checks for events or tasks in a queue and executes them one by one.

• Event loop helps prevent blocking of the main thread by allowing non-blocking execution of tasks.

• Popular exam...read more

Callback is a function passed as an argument to another function to be executed later, while a promise is an object representing the eventual completion or failure of an asynchronous operation.

• Callback is used in traditional asynchronous programming, while promises are used in modern asynchronous programming.

• Callbacks can lead to callback hell or pyramid of doom, while promises provide better readability and error hand...read more

Middlewares in Node.js are functions that have access to the request and response objects, and can modify or terminate the request-response cycle.

• Middlewares are functions that are executed in the middle of the request-response cycle.

• They can perform tasks like parsing request data, logging, authentication, etc.

• Middlewares can be added using app.use() method in Express framework.

• Example: app.use(bodyParser.json()) to p...read more

Event emitter is a pattern used to handle and respond to events in software development.

• Event emitter is a design pattern commonly used in Node.js for handling events.

• It allows objects to subscribe to events and be notified when those events occur.

• Event emitter is often used for asynchronous programming and decoupling components.

• Example: EventEmitter class in Node.js can be used to create custom events and handle them.