Lloyds Technology Centre Interview Questions and Answers

Function declaration is hoisted and can be called before it's defined, while function expression is not hoisted and must be defined before it's called.

• Function declaration is hoisted, function expression is not

• Function declaration can be called before it's defined, function expression must be defined before it's called

• Function declaration syntax: function myFunction() {}, function expression syntax: const myFunction =

Event Looping in JS is the mechanism that allows JavaScript to handle asynchronous operations by executing callback functions in a non-blocking way.

• Event Loop is responsible for executing code, collecting and processing events, and executing queued sub-tasks.

• JS is single-threaded, so Event Loop helps in managing asynchronous operations without blocking the main thread.

• Tasks are added to the call stack, then executed an...read more

Error boundaries in JS help catch and handle errors in React components.

• Error boundaries are React components that catch JavaScript errors anywhere in their child component tree.

• They log errors and display a fallback UI instead of crashing the whole app.

• To create an error boundary, define a new component with componentDidCatch(error, info) method.

• Use error boundaries sparingly as they only catch errors in components be...read more

Mock test cases using jest and react-testing library

• Use jest.fn() to create mock functions for testing

• Use jest.mock() to mock dependencies

• Use render() from react-testing library to render components for testing

• Use fireEvent() from react-testing library to simulate user interactions

• Use expect() from jest to make assertions on test results

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 transformation, security, and routing

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

I/O streams are channels through which data can be transferred between a program and an external source or destination.

• I/O streams can be used for reading input from a keyboard or file

• I/O streams can be used for writing output to a screen or file

• I/O streams can be used for network communication

A callback is a function that is passed as an argument to another function and is executed after a specific event occurs.

• Used in asynchronous programming to handle responses or events

• Allows for more flexible and modular code

• Commonly used in JavaScript for event handling