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A Comprehensive Guide for Migrating from AngularJS to Angular

February 9, 2024

Table Of Content

Navigating the End-of-Life of AngularJS

The Imperative of Migration

Advantages of Migrating to Angular

  • Enhanced Performance:
    Leveraging modern web technologies, Angular provides a more efficient and scalable framework, ensuring applications run smoother and faster.
  • Robust Security Features: With built-in protection against common web vulnerabilities, Angular offers a secure environment for developing and deploying web applications.
  • Access to Cutting-Edge Features: Angular’s active development means access to the latest web development features, facilitating the creation of dynamic, modern web applications.

Transitioning to Angular: A Leap Forward

Unleashing Performance Enhancements

  • Streamlined Change Detection: Angular’s refined change detection mechanism boosts application responsiveness.
  • Hierarchical Dependency Injection: A sophisticated system that optimizes execution and rendering, enhancing application speed.

Fortifying Security

  • Built-in Protection:
    Angular offers robust defenses against common web vulnerabilities, ensuring a secure foundation for web applications.
  • Modern Security Practices:
    Incorporating the latest security protocols to safeguard against emerging threats.

Embracing New Features

  • Access to Latest Innovations:
    Angular’s active development cycle introduces new features and improvements, keeping applications at the cutting edge.
  • Rich Ecosystem and Tools:
    A vibrant ecosystem of tools and libraries extends Angular’s functionality, supporting a wide range of development needs.

Assessing Your AngularJS Application

Understanding Your Application’s Landscape

  • Analyzing Application Size and Complexity:
    Gauge the scale and intricacy of your AngularJS application. Assess the number of lines of code, components, services, and modules to understand the effort required for migration.
  • Codebase Organization Review:
    Examine how the AngularJS application is structured. Consider the organization of files, modularity, and use of coding standards. A well-organized codebase can simplify the migration process.

Identifying Dependencies and External Libraries

  • Dependencies Inventory:
    List all dependencies and external libraries your AngularJS project relies on. This includes third-party UI components, utility libraries, and any integrations with external services.
  • Library Compatibility Check: Determine the compatibility of these dependencies with Angular. Identify which libraries have Angular equivalents or need to be replaced with alternatives that support Angular.

Migration Feasibility and Strategy

  • Full vs. Partial Migration Decision: Based on the application assessment, decide whether a full migration or a phased approach is more viable. Consider factors like critical functionality, user experience, and project timelines.
  • Resource Allocation and Timeline Estimation:
    Estimate the resources (team size, skills required) and time needed for migration. Factor in the learning curve for Angular, code rewriting, and testing phases.

Choosing a Migration Strategy

Exploring Migration Approaches

  • Big Bang Rewrite: This approach involves completely rewriting your application from AngularJS to Angular. It’s the most straightforward in terms of development, as it avoids the complexity of running AngularJS and Angular side by side. However, it requires significant effort and resources, and the application might be offline or in reduced functionality mode during the migration.
  • Hybrid Upgrade with NgUpgrade: NgUpgrade allows you to run AngularJS and Angular simultaneously in the same application, enabling a gradual migration. This method is suitable for large applications where a complete rewrite is impractical. It allows you to upgrade components or services incrementally while keeping the application fully operational.
  • Gradual Component-by-Component Migration: Similar to the hybrid upgrade, this strategy focuses on migrating individual components or modules from AngularJS to Angular. It’s ideal for applications with a modular structure, allowing for a piecemeal approach without disrupting the entire ecosystem.

Assessing Suitability and Planning

  • Application Size and Complexity:
    Smaller applications or those with a clear modular structure may benefit from a big bang rewrite or component-by-component migration. Larger, more complex applications might necessitate a hybrid approach for practical and operational reasons.
  • Timeline and Resources:
    The urgency of the migration and available resources will also influence the choice. A big bang rewrite, while faster once completed, requires significant downtime and resources. Hybrid and gradual migrations allow for more flexibility, spreading the workload over time.
  • Risk Tolerance: Evaluate the organization’s tolerance for risk. A big bang approach may introduce significant risks if not managed properly, whereas gradual approaches can mitigate risk by maintaining operational stability throughout the migration process.

Recommended Resources

  • Angular Migration Guide:
    Official Angular documentation provides comprehensive guides and best practices for migrating from AngularJS to Angular.
  • NgUpgrade Documentation: For those considering a hybrid approach, the NgUpgrade library documentation offers valuable insights into setup and integration between AngularJS and Angular.
  • Community Case Studies: Look for case studies and experiences shared by other organizations that have undergone the migration process. These can provide practical insights and lessons learned.

Setting Up Your Angular Development Environment

Installing and Configuring Angular CLI

  • Installation: Begin by installing Node.js, which includes npm (Node Package Manager), essential for managing Angular and its dependencies. After setting up Node.js, install the Angular CLI globally on your machine using npm.npm install -g @angular/cli

Creating a New Angular Project

  • Generate New Project:
    Create a new Angular project by running the following command in your terminal:


“ng new project-name”

Follow the prompts to set up your project preferences, such as enabling strict type checking, choosing a stylesheet format, etc.

Understanding Key Components:

  • Modules:
    Angular organizes applications into modules. Each module serves as a container for a related set of capabilities, including components, services, and more. The root module is known as AppModule.
  • Components: Components are the fundamental building blocks of Angular applications. Each component controls a part of the screen called a view. A component comprises a TypeScript class, an HTML template, and styles.
  • Services:
    Services are classes that handle data logic and business rules. They’re typically used for data fetching, logging, and other functionalities shared across components.

Managing Existing Resources and Assets

  • Integrating Assets:
    Migrate static assets (images, stylesheets, scripts) from your AngularJS application into the Angular project’s assets folder. Angular CLI projects are configured to automatically serve and bundle assets from this directory.
  • Refactoring Code:
    Begin refactoring your AngularJS code to fit Angular’s architecture. This involves rewriting components, services, and other entities to utilize Angular’s syntax and file structure.
  • Dependency Management: Review and migrate third-party libraries and dependencies. Use npm to install Angular-compatible versions of these libraries, and update your code to use the new imports and APIs as needed.

Migrating Components and Services

Understanding Angular Concepts

  • Components in Angular: Angular components are the core building blocks of the application’s UI. Each component manages a part of the UI through its template (HTML) and class (TypeScript), where the class defines behavior and the template defines the view. This is a shift from AngularJS, where directives were often used to control DOM elements directly. Angular components are more encapsulated and modular.
  • Services in Angular: Services in Angular are classes designed to handle data logic, APIs, and reusable business logic independently of components. Unlike AngularJS, where services, factories, and providers could be used interchangeably with subtle differences, Angular standardizes this concept into a single, unified service class, injectable across components and modules.
  • Directives in Angular:
    Directives are instructions for the DOM. While components control entire areas of the UI, directives allow you to manipulate individual elements. Angular retains the concept of directives but separates them into structural (alter layout by adding/removing elements) and attribute directives (change the appearance or behavior of an element).

Translating AngularJS to Angular

  • Components Migration: When migrating AngularJS components (directives used as components), focus on creating Angular components with a clear separation of concerns. Translate the template (HTML) and the controller (JavaScript) into Angular’s template and TypeScript class. Pay attention to lifecycle hooks, as Angular provides different hooks from AngularJS for managing component lifecycle events.
  • Services Migration: Convert AngularJS services (services, factories) into Angular services by creating classes decorated with @Injectable(). These services can then be injected into components and other services through Angular’s dependency injection system. Ensure to migrate any AngularJS-specific code, such as $http requests to Angular’s HttpClient.
  • Directives Migration: For custom directives in AngularJS that manipulate the DOM, assess whether they can be replaced with Angular’s built-in directives. If custom functionality is needed, create attribute directives in Angular by defining classes with the @Directive() decorator.

Utilizing NgUpgrade for Hybrid Applications

  • Hybrid Approach:
    The NgUpgrade library enables you to run AngularJS and Angular side by side, allowing for a gradual migration. You can upgrade services and components incrementally, facilitating a smoother transition without the need to overhaul the entire application at once.

Strategies for Gradual Migration:

  • Upgrade Services First:
    Begin by upgrading injectable services, as they often have the least dependencies on AngularJS-specific functionality and can be easily provided to both AngularJS and Angular components.
  • Component Upgrade: Use the downgradeModule to bootstrap AngularJS components inside Angular applications or the UpgradeModule to bootstrap Angular components inside AngularJS applications. This allows for the incremental replacement of components.

Data Handling and Routing

Angular’s Routing Mechanism

Angular’s routing system is a powerful and integrated part of the platform, designed to handle navigation from one view to the next as users perform application tasks. This is a significant evolution from AngularJS’s $routeProvider and ngRoute module, offering more flexibility and features.

  • Configuration-Based: Angular uses a configuration-based routing system, where routes are defined in a module (typically AppRoutingModule). This approach allows for lazy loading of feature modules, improving application performance by loading code only when needed.
  • Route Guards:
    Angular introduces route guards, enabling fine-grained control over navigation. You can protect routes, require certain conditions to be met (like authentication), and perform complex routing logic that was harder to implement in AngularJS.
  • Path Matching Strategies:
    Angular provides advanced path matching strategies, supporting complex routing scenarios including wildcard routes and redirect paths.

Adapting Data Fetching and Manipulation

  • HttpClient Module: Angular’s HttpClient module replaces AngularJS’s $http service, offering a more powerful and flexible API for making HTTP requests. Migrate existing data fetching logic to use HttpClient, taking advantage of its support for typed responses, interceptors, and RxJS Observables for handling asynchronous operations.
  • RxJS Observables: Angular extensively uses RxJS Observables, a shift from AngularJS’s promise-based approach. Observables offer more powerful and versatile ways to handle asynchronous data flows, such as retrying failed requests, combining multiple data streams, and transforming data before consumption.

Managing State and Data Flow

  • Services and Dependency Injection: Leverage Angular’s service classes and dependency injection to manage state and share data across components. This approach is similar to AngularJS but with a more streamlined and consistent system.
  • State Management Libraries:
    For complex applications, consider using state management libraries like NgRx or Akita. These libraries provide patterns and tools for managing global state in a predictable way, inspired by Redux’s principles of actions, reducers, and store.
  • Component Communication:
    For component-to-component communication, Angular continues to use input and output bindings, allowing data to flow unidirectionally from parent to child components and events to bubble from children to parents. This promotes a clean and maintainable data flow architecture.

Testing and Deployment

Testing and quality assurance are critical throughout the migration process from AngularJS to Angular, ensuring that the application remains stable, performant, and bug-free as you transition.

Thorough Testing During Migration

  • Incremental Testing: As you migrate components, services, or modules, test them incrementally. This approach helps identify issues early, making them easier to address.
  • Automated Regression Testing: Implement automated regression tests to ensure that new changes do not break existing functionality. This is crucial during a migration, where changes are frequent and significant.

Testing Techniques in Angular

  • Unit Testing:
    Angular is designed with testing in mind, offering a robust framework for unit testing components, services, and pipes. Utilize Jasmine for writing test specs and Karma as the test runner. Angular’s testing utilities, such as TestBed and async, simplify mocking dependencies and asynchronous testing.
  • End-to-End (E2E) Testing:
    For testing the application as a whole, including its interaction with back-end services and databases, employ end-to-end testing frameworks like Protractor. E2E tests simulate real user scenarios, verifying that the application behaves as expected in a production-like environment.
  • Debugging Techniques: Leverage Angular’s development tools for debugging. The Angular DevTools for Chrome and Firefox make it easier to inspect and debug applications. Use breakpoints, console logs, and the debugging features in your IDE to troubleshoot issues.

Deploying to Production

  • Optimization and Build: Before deployment, use the Angular CLI to build an optimized version of your application. Run ng build –prod to enable ahead-of-time (AOT) compilation, minification, and tree shaking, reducing the size and improving the performance of your application.
  • Environment Configuration:
    Ensure that your production environment is correctly configured for Angular. This includes setting up server-side URL rewriting to support Angular’s HTML5 mode routing.
  • Continuous Integration and Deployment (CI/CD): Implement a CI/CD pipeline to automate testing and deployment. Tools like Jenkins, GitLab CI, and GitHub Actions can automate the build, test, and deploy processes, ensuring that your application is always in a deployable state.
  • Monitoring and Feedback Loop: After deployment, monitor your application for performance, errors, and usability. Tools like Google Analytics, Sentry, and LogRocket can provide insights into how your application is being used and help identify areas for improvement.


Migrating from AngularJS to Angular is a significant undertaking that can bring substantial benefits to your web applications, including improved performance, enhanced security, and access to modern web development features. This comprehensive guide has walked you through the critical steps of the migration process, from initial assessment and planning to deployment and post-launch considerations. By understanding the differences between AngularJS and Angular, choosing the right migration strategy, and methodically testing and deploying your application, you can ensure a successful transition. Remember, migration is not just about moving code from one framework to another; it’s an opportunity to improve, optimize, and future-proof your application. With careful planning, incremental testing, and leveraging Angular’s powerful ecosystem, your migrated application can achieve greater scalability, maintainability, and user satisfaction.

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