AngularJS is a popular JavaScript framework developed by Google for building dynamic web applications. It extends HTML with additional attributes and makes it more responsive to user actions. When preparing for an AngularJS interview, it’s essential to understand key concepts like directives, controllers, services, and data binding. Be prepared to discuss two-way data binding, dependency injection, and the differences between AngularJS and Angular. Practice coding examples and be ready to explain your thought process. This guide provides common AngularJS interview questions and answers to help you ace your interview.
AngularJS Interview Questions and Answers
1. Describe AngularJS and point out its main features.
An open-source framework for front-end web applications, AngularJS is kept up to date by developers and Google. It contributes to the development of dynamic, single-page applications (SPAs) by adding new functionality to HTML and using expressions to bind data to HTML components.
Important AngularJS Features:
- MVC Architecture: Divides the application into Model, View, and Controller to provide a more organised layout.
- Two-Way Data Binding: Maintains automatic synchronisation between the model and view.
- Directives: These unique properties, such as ng-model and ng-repeat, provide HTML new possibilities.
- Expressions: Enables data embedding and basic computations within HTML.
- Filters: Filters are used to format visible data, such as dates or currencies.
- Services: Reusable parts used for routine operations such as sending HTTP requests.
2. What is scope in Angular JS?
In AngularJS, Scope is an object that connects the controller and the view. It holds the model data and allows for two-way data binding, meaning changes in the model automatically update the view and vice versa. Scopes can also contain functions, manage data inheritance, handle events, and provide isolation for directives, ensuring organized and dynamic applications.
3. What do the services represent in AngularJS?
In AngularJS, services are singleton objects or functions designed to organize and share code across your application. They provide reusable functionality that can be injected into controllers, directives, filters, and other services. Examples include $http for HTTP requests, $route for route management, and $timeout for timing functions. Services promote modular, maintainable, and testable code.
4. What is Data Binding in AngularJS?
Data Binding in AngularJS is a feature that synchronizes data between the model and the view. This two-way binding means that any changes to the model update the view, and any changes in the view update the model. It allows for a seamless and interactive user experience without the need for manual DOM manipulation.
5. How many types of data bindings are there in AngularJs?
In AngularJS, there are three types of data binding:
- One-way Binding ({{}}): Also known as interpolation, it binds data from the model to the view. For example, {{name}} will display the value of name in the view.
- Two-way Binding (ng-model): It establishes a synchronization between the model and the view. Changes in the model update the view, and changes in the view update the model. For example, ng-model=”name” binds the input field to the name model.
- Event Binding (ng-click, ng-change, etc.): It binds DOM events to actions in the controller. For example, ng-click=”submit()” will call the submit() function in the controller when the element is clicked.
6. Differences between one-way binding and two-way binding
| Aspect | One-way Binding | Two-way Binding |
| Data Flow | One-directional: from model to view | Bi-directional: from model to view and vice versa |
| Update Handling | Changes in model update the view | Changes in model update the view; changes in view update the model |
| Complexity | Simpler, involves one direction of data flow | More complex due to bidirectional data flow |
| Performance | Often offers better performance | May have slightly lower performance due to bidirectional updates |
| Use Cases | Suitable for displaying static data | Suitable for real-time synchronization between model and view, such as form inputs |
7. What are directives?
In AngularJS, directives are markers on DOM elements that trigger certain behaviors or transformations. They extend HTML with new attributes or elements, allowing developers to create reusable components, manipulate the DOM, apply behavior to elements, and more. Directives play a crucial role in enhancing the functionality and modularity of AngularJS applications.
8. What are Expression in AngularJS
In AngularJS, expressions are snippets of code that are usually placed in double curly braces {{ }} within HTML attributes, elements, or text. They are evaluated by AngularJS and are typically used to bind data from the controller to the view, enabling dynamic rendering of content. Expressions can contain variables, operators, and function calls, allowing for data manipulation and formatting directly in the HTML template.
9. What AngularJS routing does?
AngularJS routing enables the creation of single-page applications (SPAs) by dynamically loading content into the view based on the URL. It allows developers to define different routes corresponding to different views or templates, and AngularJS handles the navigation between these views without reloading the entire page. This results in a smoother and more responsive user experience, akin to traditional multi-page applications.
10. Mention some advantages of using the AngularJS framework.
AngularJS offers several advantages:
- Two-way Data Binding: Simplifies synchronization between the model and the view, reducing the need for manual DOM manipulation.
- Modular Architecture: Encourages modular development through components, directives, and services, promoting code reusability and maintainability.
- Dependency Injection: Facilitates the management of dependencies, making code more testable and modular.
- Directives: Allows the creation of custom HTML tags and attributes, enabling the creation of reusable UI components.
- Routing: Supports client-side routing, enabling the creation of single-page applications (SPAs) with smooth navigation.
- Form Validation: Provides built-in form validation features, making it easier to create robust and user-friendly forms.
- Community and Ecosystem: Has a large and active community, along with a rich ecosystem of libraries, tools, and resources.
- MVVM Architecture: Follows the Model-View-ViewModel (MVVM) architectural pattern, promoting separation of concerns and easier code maintenance.
- Testing Support: Offers support for unit testing and end-to-end testing, making it easier to ensure code quality and reliability.
- Performance Optimization: Provides features like lazy loading, ahead-of-time (AOT) compilation, and tree shaking to optimize performance and reduce bundle size.
11. How to share data between controllers in AngularJS?
To share data between controllers in AngularJS, the common practice involves utilizing services. These services, acting as singletons, facilitate the storage and access of data across various controllers. By injecting the same service into different controllers, seamless data sharing is achieved, promoting modularity and maintaining a clear separation of concerns within AngularJS applications.
12. Explain what a digest cycle is in AngularJS.
In AngularJS, a digest cycle is like a loop that Angular runs to keep track of changes in data. During each cycle, Angular checks all the expressions (or bindings) in the application to see if any values have changed since the last check. If it finds any changes, it updates the corresponding parts of the webpage to reflect those changes. This process ensures that the view is always in sync with the underlying data model.
13. What is an AngularJS module?
An AngularJS module is like a container for the different parts of your AngularJS application. It groups together components like controllers, services, directives, filters, and more. Modules help organize your code, making it easier to manage and reuse. They also facilitate the process of configuring your app and specifying dependencies between different parts of your application. Overall, modules play a central role in structuring AngularJS applications.
14. How does routing work in AngularJS?
In AngularJS, routing works by mapping URLs to different views or templates within a single-page application (SPA). When a user navigates to a specific URL, AngularJS’s routing module intercepts the request and loads the corresponding view or template without reloading the entire page. This allows for a smoother user experience similar to traditional multi-page applications, where different content is displayed based on the URL, while still maintaining the benefits of a single-page application architecture.
15. What is the difference between Angular and AngularJS?
| Aspect | AngularJS (Angular 1) | Angular (Angular 2 and above) |
| Architecture | Follows MVC (Model-View-Controller) architecture | Follows component-based architecture |
| Language | Primarily uses JavaScript | Uses TypeScript as the primary language |
| Data Binding | Primarily uses two-way data binding | Emphasizes unidirectional data flow |
| Performance | Generally lower performance | Offers improved performance |
| Tooling Support | Limited tooling support | Enhanced tooling support |
| Scalability | Limited scalability | Offers better scalability |
| Dependency Injection | Supports dependency injection | Supports dependency injection |
| Learning Curve | Moderate learning curve | Slightly steeper learning curve |
| Community Support | Established community support | Active community support |
| Mobile Support | Limited support for mobile development | Better support for mobile development |
Conclusion
In summary, the article on “AngularJS Interview Questions and Answers” offers a valuable repository of information for both interviewers and candidates. Covering essential topics like data binding, directives, and routing, it provides a comprehensive understanding of AngularJS concepts. Whether preparing for an interview or evaluating candidates’ skills, these questions serve as a useful resource to assess proficiency in AngularJS development.
