AngularJS vs. Angular 2

Author: Amey Parab | Date: 12/02/2016

Before diving into the differences, let's have a quick overview of both frameworks. AngularJS (also known as Angular 1) is a JavaScript-based open-source front-end web framework. Angular 2 is a complete rewrite of AngularJS, and it's based on TypeScript.

Both frameworks are used for building dynamic, single-page web applications (SPAs). However, Angular 2 represents a significant shift in how we build web applications, offering substantial architectural changes and performance improvements.

Key Differences

• Language:
  • AngularJS: Primarily uses JavaScript.
  • Angular 2: Uses TypeScript, a superset of JavaScript that adds static typing, classes, and interfaces. This leads to more maintainable and scalable code. This is a major change for developers coming from AngularJS.
• Architecture:
  • AngularJS: Follows a Model-View-Controller (MVC) architecture, which can become complex in larger applications.
  • Angular 2: Employs a component-based architecture. Applications are now built as a tree of reusable components, which simplifies development and improves maintainability. This is a fundamental shift in how Angular applications are structured.
• Performance:
  • AngularJS: Performance can degrade in complex applications with many bindings due to its digest cycle.
  • Angular 2: Offers significantly improved performance through a more efficient change detection mechanism. It also benefits from Ahead-of-Time (AOT) compilation, which can further boost performance. We're seeing substantial speed improvements in Angular 2.
• Mobile Support:
  • AngularJS: Was not originally designed with mobile in mind, and performance on mobile devices could be an issue.
  • Angular 2: Is designed with mobile in mind. It is optimized for mobile performance and supports building Progressive Web Applications (PWAs). This is a key focus for the Angular team.
• Learning Curve:
  • AngularJS: Has a gentler learning curve for those already familiar with JavaScript.
  • Angular 2: Has a steeper learning curve, especially with the introduction of TypeScript, but provides a more structured and consistent approach to development. The component-based architecture, while initially more to learn, should lead to more maintainable code in the long run.
• Routing:
  • AngularJS: Uses `$route` service for routing.
  • Angular 2: Uses a new and more powerful routing module.
• Change Detection:
  • AngularJS: Uses a "dirty checking" mechanism, which can be inefficient.
  • Angular 2: Uses a more efficient change detection tree.

In summary, Angular 2 offers significant improvements in terms of performance, architecture, and mobile support compared to AngularJS. While AngularJS is still a viable option for existing projects, Angular 2 is the future of Angular development, and we recommend it for new projects.

Adopting Angular 2: If you're starting a new project, we strongly recommend beginning with Angular 2. For existing AngularJS projects, the upgrade path can vary. For small projects, a rewrite might be feasible. For larger applications, a gradual migration strategy, using tools and techniques provided by the Angular team, is often the best approach. This allows you to update parts of your application incrementally, reducing risk and complexity. The Angular team is providing guidance and tools to help with this transition.

Helpful Resources

• Angular Upgrade Guide - Official documentation on upgrading from AngularJS to Angular.