Ericsson Senior Devops Engineer Interview Questions and Answers

Closure is a function that has access to variables in its outer scope, even after the outer function has returned.

• A closure can be used to create private variables and methods in JavaScript.

• Closures can be used to implement partial application and currying.

• Event listeners and callbacks often use closures to maintain state between function calls.

• Closures can be used to create memoized functions that cache their results

Callbacks hell is a situation where nested callbacks make code hard to read and maintain. Promises, observables, and async/await are solutions to this problem.

• Callbacks hell occurs when there are too many nested callbacks in code.

• Promises are a way to handle asynchronous operations in JavaScript.

• Observables are similar to promises but can handle multiple values over time.

• Async/await is a syntax for writing asynchronous

Higher order functions are functions that take other functions as arguments or return functions as their result.

• Higher order functions allow for more flexible and reusable code.

• They can be used for tasks such as filtering, mapping, and reducing arrays.

• Examples include Array.prototype.map(), Array.prototype.filter(), and Array.prototype.reduce().

OOPs in JavaScript is a programming paradigm that uses objects to represent real-world entities. Functional programming is a paradigm that uses functions to perform tasks.

• OOPs in JavaScript involves creating objects that have properties and methods.

• Functional programming involves creating functions that take input and produce output without modifying the input.

• OOPs focuses on encapsulation, inheritance, and polymorphis...read more

Event loop is a mechanism that allows JavaScript to perform non-blocking I/O operations.

• Event loop is responsible for handling asynchronous callbacks in JavaScript.

• Tasks in the queue can be either microtasks or macrotasks.

• Microtasks are executed before macrotasks.

• Examples of macrotasks include setTimeout, setInterval, and I/O operations.

• Examples of microtasks include Promise callbacks and mutation observer callbacks.

Output of the code in JavaScript

• Need to see the code to determine output

• Output can vary based on input and logic

• Can use console.log() to print output

Browsers use rendering engines to interpret HTML, CSS, and JavaScript to display web pages.

• Browsers use rendering engines to interpret HTML, CSS, and JavaScript.

• The rendering engine parses the HTML and creates a DOM tree.

• The rendering engine then applies CSS rules to the DOM tree to create a render tree.

• The render tree is then laid out to determine the position of each element on the page.

• Finally, the rendering engine ...read more