User Interface and Angular Developer Interview Questions and Answers

Pure pipes are stateless and only depend on input data, while impure pipes have internal state and can have side effects.

• Pure pipes are faster and more efficient than impure pipes.

• Pure pipes are used for simple transformations of data, while impure pipes are used for more complex transformations.

• Examples of pure pipes include currency and date formatting, while examples of impure pipes include filtering and sorting.

• To mark a pipe as pure, add the @Pipe({pure: true}) decorator...read more

Observables are streams of data that can be subscribed to, while promises are a one-time operation that returns a single value.

• Observables can emit multiple values over time, while promises only return a single value.

• Observables can be cancelled, while promises cannot.

• Observables are lazy, meaning they only execute when subscribed to, while promises execute immediately.

• Observables have operators that can transform, filter, and combine data, while promises do not.

• Observables a...read more

Interceptors are used to intercept HTTP requests and responses to perform transformations or error handling.

• Interceptors can be used to add headers to outgoing requests or handle errors in incoming responses.

• They can also be used to modify the request or response before it is sent or received.

• Interceptors can be global or specific to a certain request or response.

• They are useful for implementing authentication, caching, or logging in an application.

• Example: Adding an authoriz...read more

Dependency Injection is a design pattern used in Angular to inject dependencies into a component or service.

• It allows for easier testing and maintenance of code

• Dependencies are injected through the constructor of a component or service

• Angular has its own Dependency Injection system built-in

• Services can be shared across multiple components through Dependency Injection

Directives are markers on a DOM element that tell AngularJS to attach a specified behavior to that DOM element.

• Directives are used to create reusable components.

• They can be used to manipulate the DOM.

• They can be used to add behavior to an existing DOM element.

• They can be used to create custom attributes.

• Examples include ng-repeat, ng-model, and ng-show.

Promises are used for asynchronous operations that return a single value, while Observables are used for asynchronous operations that return multiple values over time.

• Promises are eager and execute immediately upon creation

• Observables are lazy and only execute when subscribed to

• Promises can only return a single value

• Observables can return multiple values over time

• Promises cannot be cancelled once they are created

• Observables can be cancelled by unsubscribing

• Promises are not ca...read more

Event loop is a mechanism in programming that allows for asynchronous execution of code.

• Event loop is responsible for handling and executing events in a non-blocking manner.

• It continuously checks the event queue and processes events one by one.

• Event loop is commonly used in JavaScript to handle asynchronous operations like setTimeout, setInterval, and AJAX requests.