AngularJS Interview Questions
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AngularJS Interview Questions
AngularJS Interview Questions: A Comprehensive Guide
AngularJS, developed by Google, is a powerful JavaScript framework used for building dynamic web applications. Though newer versions of Angular have since been released, AngularJS remains an essential technology for many legacy systems. For developers preparing for AngularJS interviews, understanding the framework's core concepts and being able to articulate them clearly is crucial. This guide covers essential AngularJS interview questions, providing in-depth explanations to help you prepare thoroughly.
1. What is AngularJS?
AngularJS is an open-source JavaScript framework designed to create dynamic single-page applications (SPAs). It extends HTML with additional features and provides a more structured way to build web applications through its modular architecture. AngularJS simplifies the development process by offering two-way data binding, dependency injection, and directives.
Key Concepts:
- Two-Way Data Binding: Synchronizes the model and view, ensuring that changes in the model are automatically reflected in the view and vice versa.
- Directives: Special tokens in the markup that tell the library to do something to the DOM.
- Dependency Injection (DI): A design pattern used to manage dependencies within an application, promoting modularity and testability.
2. Explain the MVC Architecture in AngularJS.
AngularJS uses the Model-View-Controller (MVC) architecture to separate the concerns of an application. This design pattern divides an application into three interconnected components:
- Model: Represents the data and business logic of the application. It handles data operations and business rules, typically interacting with backend services or APIs.
- View: The user interface of the application. It presents data to the user and reflects the changes in the model through AngularJS's data binding.
- Controller: Acts as an intermediary between the Model and View. It manages user input, updates the model, and modifies the view accordingly.
In AngularJS, controllers manage the scope, which is an object that links the controller and the view. The scope serves as a bridge, providing data and methods for the view to interact with the model.
3. What are Directives in AngularJS?
Directives in AngularJS are special tokens that extend HTML with custom behavior or manipulate the DOM in some way. They are a core feature of AngularJS, allowing developers to create reusable components and enhance the HTML capabilities.
Types of Directives:
- Component Directives: Define reusable components with their own templates and controllers. They encapsulate HTML, CSS, and JavaScript into a single entity.
- Attribute Directives: Change the behavior or appearance of an HTML element. These are typically used to add functionality to elements.
- Structural Directives: Alter the layout of the DOM by adding or removing elements. They include directives like ngIf, ngFor, and ngSwitch.
Directives help in creating modular, maintainable code by allowing the definition of custom behaviors and components.
4. What is Two-Way Data Binding in AngularJS?
Two-way data binding is a key feature of AngularJS that automatically synchronizes data between the model and the view. This means that any changes to the model are reflected in the view, and any changes in the view are updated in the model.
Mechanism:
- AngularJS establishes a binding between the view and the model through the $scope object.
- When the model's data changes, AngularJS updates the view automatically.
- Similarly, user interactions or changes in the view are reflected back in the model without additional code.
This feature simplifies the development process by eliminating the need for manual DOM manipulation and reducing boilerplate code.
5. What is Dependency Injection in AngularJS?
Dependency Injection (DI) is a design pattern used in AngularJS to manage and provide dependencies within an application. DI helps in creating a modular, testable codebase by injecting dependencies (such as services or factories) into components rather than hard-coding them.
Key Concepts:
- Injector: AngularJS uses an injector to create and manage dependencies. The injector resolves and provides the required services or objects to components like controllers and directives.
- Providers: AngularJS defines dependencies through providers, which are responsible for creating and configuring services.
- Injection: Components declare their dependencies via the constructor or function parameters, and AngularJS's injector provides them automatically.
Dependency Injection promotes loose coupling and enhances testability by allowing the replacement of real dependencies with mocks or stubs during testing.
6. Explain the Role of $scope in AngularJS.
The $scope object is a central concept in AngularJS, acting as a bridge between the controller and the view. It represents the application model and is used for data binding, providing the context in which expressions are evaluated.
Key Functions:
- Data Binding: $scope is used to bind data between the controller and the view. Any changes in the $scope object are automatically reflected in the view.
- Watchers: AngularJS watches the $scope properties for changes and triggers updates to the view when necessary.
- Inheritance: Child scopes inherit properties from their parent scopes, allowing for hierarchical data structures.
By using $scope, AngularJS enables dynamic updates and interactions within the application, making it easier to manage and display data.
7. What is the $digest Cycle in AngularJS?
The $digest cycle is an internal mechanism in AngularJS responsible for updating the view when the model changes. It is a core part of AngularJS's data binding system, ensuring that the view remains in sync with the model.
Process:
- AngularJS maintains a list of watchers that track changes to $scope properties.
- When a change is detected, the $digest cycle is triggered, and AngularJS iterates through the list of watchers.
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- Each watcher checks for changes and updates the view if necessary.
The $digest cycle runs automatically in response to events such as user input or asynchronous operations, ensuring that the application remains responsive and up-to-date.
8. Describe AngularJS Filters and Their Uses.
Filters in AngularJS are used to format and transform data before it is displayed in the view. They provide a way to modify the appearance of data without altering the underlying data model.
Types of Filters:
- Built-in Filters: AngularJS includes several built-in filters for common tasks, such as formatting dates, numbers, and currencies, or filtering lists of items.
- Custom Filters: Developers can create their own filters to perform specific transformations or formatting operations.
Filters are applied in expressions and directives, allowing for dynamic data presentation and user interface customization.
9. What is a Service in AngularJS?
A service in AngularJS is a singleton object that provides a way to share data and functionality across different parts of an application. Services are used to handle business logic, interact with backend APIs, and manage application state.
Characteristics:
- Singleton: A single instance of a service is created and shared throughout the application.
- Reusable: Services can be injected into controllers, directives, and other services, promoting code reuse and modularity.
Services are defined using AngularJS's service API and are typically used to encapsulate logic that is shared across multiple components.
10. What are AngularJS Promises?
Promises in AngularJS are objects that represent the eventual completion (or failure) of an asynchronous operation. They provide a way to handle asynchronous tasks, such as data retrieval from a server, and manage the results or errors.
Key Concepts:
- Promise States: A promise can be in one of three states: pending, resolved, or rejected. These states represent the progress of the asynchronous operation.
- Methods: Promises have methods like then, catch, and finally that handle the results or errors of the asynchronous operation.
Promises simplify the management of asynchronous tasks by allowing developers to write cleaner, more readable code for handling results and errors.
11. Explain AngularJS Routing.
Routing in AngularJS is a feature that allows developers to create single-page applications (SPAs) with multiple views. It enables navigation between different views without reloading the entire page.
Key Components:
- Routes: Define the mapping between URLs and views, specifying which template and controller should be used for a given route.
- `$routeProvider`: Configures the application's routes and associates them with specific views and controllers.
Routing helps in organizing the application's structure, providing a seamless user experience by loading different views based on the application's state.
12. What is the $http Service in AngularJS?
The $http service is used to make HTTP requests to a backend server and interact with APIs. It simplifies the process of sending and receiving data, handling requests, and processing responses.
Conclusion
Preparing for an AngularJS interview involves a solid understanding of its core concepts and features. By familiarizing yourself with the MVC architecture, directives, data binding, dependency injection, and other fundamental aspects of AngularJS, you can demonstrate your proficiency and readiness for working with this powerful framework. This guide provides a comprehensive overview of essential AngularJS interview questions, equipping you with the knowledge needed to excel in your interviews and build robust web applications using AngularJS.
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