Angular.js Interview Questions and Answers for 5 years experience

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AngularJS Interview Questions and Answers

  1. What is AngularJS?

    • Answer: AngularJS is a JavaScript-based open-source front-end web application framework mainly maintained by Google and by a community of individuals and corporations to address many of the challenges encountered in developing single-page applications. It allows developers to use HTML as the template language and extend HTML’s syntax to express the application’s components clearly and succinctly. It's a structural framework for dynamic web apps.

  2. Explain the MVC architecture in AngularJS.

    • Answer: AngularJS follows the MVC (Model-View-Controller) architectural pattern. The Model represents the data, the View displays the data, and the Controller handles user interactions and updates the Model and View accordingly. This separation of concerns makes code more organized, maintainable, and testable.

  3. What are directives in AngularJS? Give examples.

    • Answer: Directives extend HTML with custom attributes, elements, and CSS classes. They allow you to create reusable components and manipulate the DOM. Examples include `ng-model`, `ng-repeat`, `ng-if`, `ng-switch`, and custom directives created by developers.

  4. Explain two-way data binding in AngularJS.

    • Answer: Two-way data binding automatically synchronizes data between the model and the view. Any changes in the model are reflected in the view, and vice-versa. This eliminates the need for manual DOM manipulation, simplifying development and improving efficiency.

  5. What are scopes in AngularJS?

    • Answer: Scopes are objects that act as bridges between controllers and views. They hold the application data and provide a way for controllers to interact with the view. They are also used for event handling and communication between different parts of the application.

  6. What are services in AngularJS? How do they promote reusability?

    • Answer: Services are singleton objects that provide specific functionalities to controllers and other parts of the application. They promote reusability by encapsulating logic and data that can be shared across multiple components. Examples include data services, logging services, and authentication services.

  7. Explain the difference between factory and service in AngularJS.

    • Answer: Both factories and services are ways to create services, but they differ in how they are defined. Factories are functions that return an object, while services are constructor functions. Factories offer more flexibility in terms of returning different objects based on dependencies or configurations.

  8. What are filters in AngularJS? Give examples.

    • Answer: Filters format data for display in the view. They transform data before it's rendered. Examples include `currency`, `date`, `lowercase`, `uppercase`, `orderBy`, and custom filters created by developers.

  9. How do you handle events in AngularJS?

    • Answer: AngularJS handles events using directives like `ng-click`, `ng-change`, `ng-submit`, etc., and by using event listeners within controllers or directives. Events are typically bound to functions within the scope, which handle the event logic.

  10. Explain dependency injection in AngularJS.

    • Answer: Dependency Injection is a design pattern where dependencies are provided to components rather than being created within them. AngularJS uses dependency injection to manage the lifecycle of services and controllers, promoting modularity, testability, and maintainability.

  11. What are promises in AngularJS?

    • Answer: Promises are objects that represent the eventual result of an asynchronous operation. They provide a way to handle asynchronous code in a more structured and manageable way, using `.then()` to handle success and `.catch()` to handle errors.

  12. Explain routing in AngularJS using $routeProvider.

    • Answer: `$routeProvider` is used to configure different routes within an AngularJS application. Each route maps a URL path to a specific view and controller. This allows for creating single-page applications with multiple views, enhancing user experience.

  13. How do you perform unit testing in AngularJS?

    • Answer: Unit testing in AngularJS typically involves using frameworks like Jasmine and Karma. Tests are written to verify the functionality of individual components (controllers, services, directives) in isolation, ensuring code quality and maintainability.

  14. What are some best practices for AngularJS development?

    • Answer: Best practices include using dependency injection effectively, keeping controllers lean, creating reusable components (directives and services), writing unit tests, following a consistent coding style, and using appropriate tools for development and deployment.

  15. How do you handle HTTP requests in AngularJS?

    • Answer: AngularJS provides the `$http` service for making HTTP requests (GET, POST, PUT, DELETE). This service handles the complexities of AJAX requests and returns promises, allowing for asynchronous handling of responses.

  16. Explain the concept of modules in AngularJS.

    • Answer: Modules are used to organize and structure the application's code. They provide a way to group related controllers, services, directives, and other components together. This improves maintainability and reduces code complexity.

  17. What is the difference between `$scope.$watch` and `$scope.$apply`?

    • Answer: `$scope.$watch` monitors changes in a specific scope property and executes a callback function when the property's value changes. `$scope.$apply` is used to update the scope from outside of Angular's context, such as in a callback from a third-party library, to trigger the digest cycle.

  18. Explain how AngularJS handles data validation.

    • Answer: AngularJS provides built-in directives and features for data validation. Directives like `ng-required`, `ng-minlength`, `ng-maxlength`, and `ng-pattern` can be used to set validation rules. Custom validation can be implemented using custom directives or by using the `$validators` object.

  19. How do you debug AngularJS applications?

    • Answer: Debugging techniques include using browser's developer tools (console logging, breakpoints), using AngularJS's built-in debugging tools (e.g., `$log` service), and employing dedicated debugging extensions for browsers.

  20. What are the advantages of using AngularJS?

    • Answer: Advantages include two-way data binding, MVC architecture, dependency injection, modularity, testability, and a large community and extensive documentation.

  21. What are the limitations of AngularJS?

    • Answer: Limitations include performance issues with large applications, digest cycle limitations, and a steeper learning curve compared to some other frameworks.

  22. How would you optimize performance in a large AngularJS application?

    • Answer: Optimization strategies include minimizing the use of watchers, using one-time binding (`::`), using appropriate filters, optimizing digest cycles, and utilizing techniques like pagination and lazy loading.

  23. Explain the difference between AngularJS and Angular (Angular 2+).

    • Answer: AngularJS (Angular 1.x) is based on JavaScript, while Angular (2+) is based on TypeScript. Angular has a component-based architecture, improved performance, and a different approach to data binding and dependency injection compared to AngularJS.

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