Most popular Angular interview questions

What is Angular and why do we use it?

Angular is an open-source complete rewrite of the AngularJS JavaScript framework developed by Google. It is used for building web applications and is based on the Model-View-Controller (MVC) architecture. Angular provides a number of features that make it easy to develop dynamic, responsive web applications.

What is the difference between AngularJS and Angular?

AngularJS is the first version of the Angular framework, released in 2010. It uses JavaScript as its primary language and is based on the Model-View-Controller (MVC) architecture. Angular was released in 2016 and is a complete rewrite of AngularJS. It uses TypeScript as its primary language and is based on the Model-View-ViewModel (MVVM) architecture.

What is TypeScript and why would you use it with Angular?

TypeScript is a superset of JavaScript that adds static typing, interfaces, and other features to the language. It is used with Angular to provide better tooling, code completion, and type checking, which can help catch errors before runtime. TypeScript also makes it easier to write more maintainable and scalable code.

What is a module in Angular?

A module is a container for a group of affiliated factors, directives, pipes, and services. It provides a context for the components to interact with each other and allows them to share data and dependencies. Modules can be used to organize an application into separate functional areas.

What is a component in Angular?

A component is a building block of an Angular application that controls a portion of the UI. It consists of a TypeScript class that defines the component's behavior and a template that defines its view. Components can be reused throughout an application and can be nested within other components.

What is TypeScript and why would you use it with Angular?

TypeScript is a superset of JavaScript that adds static typing, interfaces, and other features to the language. It is used with Angular to provide better tooling, code completion, and type checking, which can help catch errors before runtime. TypeScript also makes it easier to write more maintainable and scalable code.

What is a component in Angular?

A component is a building block of an Angular application that controls a portion of the UI. It consists of a TypeScript class that defines the component's behavior and a template that defines its view. Components can be reused throughout an application and can be nested within other components.

What is a module in Angular?

A module in angular is a container for a group of related components, directives, pipes, and services. It provides a context for the components to interact with each other and allows them to share data and dependencies. Modules can be used to organize an application into separate functional areas.

What is data binding in Angular?

Data binding is a mechanism in Angular that allows you to synchronize data between the model and the view. There are three types of data binding in Angular: one-way binding, two-way binding, and event binding. One-way binding updates the view when the model changes, while two-way binding updates the model and the view simultaneously. Event binding allows you to bind methods to events triggered by the user.

What is a service in Angular?

A service is a class in Angular that provides functionality that can be shared across multiple components. Services can be used to manage data, perform calculations, make API calls, and more. Services are typically injected into components using dependency injection.

What is dependency injection in Angular?

Dependency injection is a design pattern used in Angular to provide components with the dependencies they need to function. It allows you to decouple components from their dependencies, making them more modular and easier to test. In Angular, dependencies are provided by modules and injected into components using constructors.

What is routing in Angular?

Routing is a mechanism in Angular that allows you to navigate between different views in an application. It allows you to define routes for different components and link to those routes from other components. Routing is typically used to create single-page applications with multiple views.

What is lazy loading in Angular?

Lazy loading is a technique in Angular that allows you to load modules and components on demand, rather than loading them all at once. This can improve the performance of an application by reducing the initial load time and only loading the components that are needed at any given time. 

What is the difference between Observables and Promises?

Observables and Promises are both used for handling asynchronous operations in JavaScript, but they have different characteristics and ways of handling data.

A Promise is a special object in JavaScript that represents the eventual completion (or failure) of an asynchronous operation and returns a single value when resolved. Promises are a simple way to handle asynchronous operations and are commonly used for network requests and other time-consuming tasks. They can only have one value, and once the value is resolved, the Promise will always return that value.

On the other hand, an Observable is an object that represents a stream of data that can be observed over time. Observables can have multiple values over time and are often used for handling continuous streams of data such as user input, sensor data, or real-time events. They also provide powerful operators for transforming and manipulating the stream of data.

In summary, Promises are used for handling a single asynchronous operation and returning a single value when resolved, while Observables are used for handling continuous streams of data and can have multiple values over time.

Here are some advanced Angular interview questions:

• What is lazy loading in Angular and how do you implement it?
• What are some strategies for optimizing the performance of an Angular application?
• How do you handle state management in an Angular application?
• How do you implement server-side rendering in an Angular application?
• What are some common design patterns used in Angular development?
• How do you implement form validation in Angular?
• What are the best practices for testing Angular applications?
• How do you integrate third-party libraries and APIs into an Angular application?
• How do you implement authentication and authorization in an Angular application?
• What are some common pitfalls to avoid when developing an Angular application?
• What are AUTH Guards in Angular?
• What is Pipe in Angular?
• What are interceptors in Angular?

These questions are meant to assess your knowledge and experience with advanced Angular topics. It's important to have a solid understanding of the framework and its features, as well as experience working on real-world Angular projects. Be prepared to provide examples of your work and demonstrate your problem-solving skills during the interview process.