Angular Interview Questions

AngularJS (also known as Angular 1.x) and Angular (versions 2 and beyond) are both web application frameworks developed by Google, but they differ significantly in terms of architecture, design principles, performance, and capabilities. Here are the key differences between AngularJS and Angular:

1. Architecture:

• AngularJS:

  • MVC Framework: AngularJS follows the Model-View-Controller (MVC) architecture. The controller is responsible for processing the business logic, the view displays the data, and the model holds the data.
  • Two-Way Data Binding: AngularJS uses two-way data binding, which means that any changes in the model automatically update the view and vice versa.

• Angular:

  • Component-Based Architecture: Angular uses a component-based architecture, where the application is composed of a set of well-encapsulated, reusable components.
  • One-Way Data Binding: Angular primarily uses one-way data binding. Data flows from the model to the view, and event binding is used to propagate changes from the view to the model.

2. Language:

• AngularJS:

  • JavaScript: AngularJS is written in JavaScript and is typically used with JavaScript for developing applications.
  • Less Structure: JavaScript’s dynamic nature allows for more flexibility but less structure and type safety.

• Angular:

  • TypeScript: Angular is written in TypeScript, a statically typed superset of JavaScript. TypeScript brings features like type checking, interfaces, and classes, making the code more robust and maintainable.
  • Modern JavaScript: TypeScript compiles down to JavaScript, enabling the use of modern JavaScript features.

3. Performance:

• AngularJS:

  • Digest Cycle: AngularJS relies on a digest cycle to track changes in the scope and update the DOM. This can lead to performance bottlenecks, especially in large applications with many watchers.
  • Slower for Large Applications: As the size of the application grows, the performance can degrade due to the complexity of the digest cycle.

• Angular:

  • Ahead-of-Time (AOT) Compilation: Angular offers AOT compilation, which compiles the application during the build process, resulting in faster rendering in the browser.
  • Change Detection: Angular uses a more efficient change detection mechanism based on Zone.js, which tracks asynchronous operations and optimizes DOM updates.
  • Lazy Loading: Angular supports lazy loading, which improves performance by loading only the necessary parts of the application on demand.

4. Dependency Injection:

• AngularJS:

  • Custom DI System: AngularJS has its own dependency injection system, which is functional but less powerful compared to Angular’s.
  • Global Scope Management: Dependencies are often managed in a global scope, which can lead to issues in large applications.

• Angular:

  • Advanced DI System: Angular has a more advanced and flexible dependency injection system, which allows for better management of dependencies and services.
  • Hierarchical DI: Angular’s DI system supports hierarchical injectors, enabling scoped and modular dependency management.

5. Mobile Support:

• AngularJS:

  • Limited Mobile Support: AngularJS was primarily designed for desktop applications and offers limited support for mobile development.

• Angular:

  • Optimized for Mobile: Angular is designed with mobile-first in mind. It provides features like server-side rendering, mobile-specific optimizations, and a more compact framework size.
  • Angular Mobile Toolkit: Angular has tools and libraries specifically designed for mobile development, such as Angular Mobile Toolkit and Angular Service Worker for Progressive Web Apps (PWAs).

6. Tooling and Ecosystem:

• AngularJS:

  • Basic Tooling: AngularJS has basic tooling support, primarily through the AngularJS CLI and various third-party tools.
  • Legacy Support: AngularJS has a mature ecosystem but is considered a legacy framework with declining community support.

• Angular:

  • Angular CLI: Angular provides a robust CLI (Command Line Interface) that simplifies project setup, development, testing, and deployment.
  • Rich Ecosystem: Angular has a vibrant and growing ecosystem with extensive support for modern development practices, libraries, and tools.
  • Active Community: Angular has active community support, regular updates, and strong backing from Google.

7. Backward Compatibility:

• AngularJS:

  • No Backward Compatibility: AngularJS and Angular are not backward compatible. Upgrading from AngularJS to Angular requires a complete rewrite of the application.

• Angular:

  • Backward Compatibility: Angular maintains backward compatibility across major versions, making it easier to upgrade applications without extensive rewrites.

In Summary:

AngularJS and Angular are both frameworks developed by Google, but they differ significantly in their architecture, language, performance, dependency injection, mobile support, tooling, and ecosystem. AngularJS is based on the MVC pattern and JavaScript, while Angular uses a component-based architecture and TypeScript. Angular offers superior performance, modern tooling, and better support for mobile development compared to AngularJS. Due to these differences, Angular is generally recommended for new projects, while AngularJS remains a legacy framework with diminishing support.