30+ Angular Interview Questions And Answers

Angular is a platform and framework for building client-side applications using HTML, CSS, and TypeScript. It is used for developing single-page applications where the page does not need to reload during use. It is particularly good for data-binding, building reusable components, and handling form submissions.

In Angular, a component is a main building block. It is a class that interacts with the HTML template and acts as a controller for the view. Components have a decorator @Component() that provides metadata, including the template, styles, and selector.

Directives are instructions in the DOM. There are three types: Components, Structural directives that change the DOM layout by adding and removing DOM elements, and Attribute directives that change the appearance or behavior of an element.

Data binding is a feature that allows communication between a template (view) and its component (class). The four types of data binding in Angular are: Interpolation, Property binding, Event binding, and Two-way binding.

Pipes are simple functions used in Angular templates that transform input values to a desired output. For example, date pipe can format a date object into a readable string.

{{ currentDate | date:'medium' }}

A service in Angular is a broad category that encompasses any value, function, or feature needed by an app. A component can delegate certain tasks to services to achieve separation of concerns.

You create a service by defining a service class with the @Injectable() decorator. This ensures that the Angular dependency injection system can provide an instance of the service.

Dependency Injection (DI) is a design pattern in which a class requests dependencies from external sources rather than creating them itself. Angular's DI system provides dependencies to a class.

A module is a way to group components, services, directives, and pipes. It is used to organize code or features that belong together, making the app easier to develop and test.

Data can be passed between components using Input and Output decorators. Input allows data to be passed from parent to child, while Output allows data to be emitted from child to parent.

Common lifecycle hooks include ngOnInit(), ngDoCheck(), ngAfterContentInit(), ngAfterContentChecked(), ngAfterViewInit(), ngAfterViewChecked(), and ngOnDestroy().

TypeScript is a superset of JavaScript that adds static typing. Angular uses TypeScript because it provides more robust tools for large-scale applications, including strong typing, classes, and interfaces.

Observables provide support for passing messages between parts of your application. They are used heavily in Angular and are an essential part of working with the HTTP client and event handling.

Routing in Angular allows navigation from one view to another. Developers define paths and map them to components. The RouterOutlet directive is used to display the component for the active route.

A Promise handles a single event when an async operation completes or fails, while an Observable is like a stream and allows passing zero or more events where callback is called for each event.