AngularJS to Angular migration guide

AngularJS was an early framework to build web applications having MVC architecture and using JavaScript. However, as web development has progressed, the tools we use have also improved. Angular, with its component-based architecture, TypeScript foundation, superior performance, mobile support, advanced dependency injection system, and modular approach, has become a more robust and scalable solution for modern web development.

Though instrumental in shaping early web applications, AngularJS has now been superseded by Angular, which boasts superior features and improved alignment with modern web development best practices. The message is clear: it is high time for developers already using AngularJS to switch over to Angular, so as to take advantage of a more current, powerful and maintainable framework.

In our blog post, we explore the comprehensive process of migrating from AngularJS to Angular, providing you with essential considerations and a step-by-step guide to help you take full advantage of Angular's enhanced capabilities.

Angular JS vs. Angular: the key differences?

AngularJS and Angular, while sharing a common background, differ significantly in their architecture, language, performance, mobile support, dependency injection, and modularity. 

The following table provides a concise overview of the key distinctions between AngularJS and Angular. Following the table, you'll find a more detailed explanation of each parameter.

Architecture

AngularJS: AngularJS uses the Model-View-Controller (MVC) architecture to keep the most important parts of an application separate from one another. With such architecture, developers can divide their apps into three interconnected components, each serving a distinct role. The view handles data presentation to the user. The model defines how information appears in the app, and the controller links these two parts together by processing user input and updating the view accordingly. This division helps organize the code, however, can become cumbersome, especially for large-scale applications.

Angular: As opposed to MVC architecture, Angular uses a model that is based on components. Components in this context may be explained as independent parts that encapsulate the view, data, and logic together to make it easier to manage and reuse them. For better code organization and maintainability, every component in Angular can be considered as a little MVC structure in itself. This modularity makes Angular one of the most versatile frameworks for developing complex and scalable web applications.

Language

AngularJS: AngularJS is written in JavaScript, a dynamic, weakly typed language. While JavaScript's flexibility is an advantage, it can also lead to issues such as runtime errors and less predictable code behavior.

Angular: Angular, on the other hand, is written in TypeScript, a statically typed superset of JavaScript. TypeScript introduces static types, which help catch errors at compile time rather than at runtime. It also offers advanced features, such as interfaces, enums, and generics, improving code quality and developer productivity. The use of TypeScript in Angular leads to more robust and maintainable codebases.

Performance

AngularJS: AngularJS uses two-way data binding, which automatically synchronizes the data between the model and the view. This approach makes the development process easier, however, frequent updates and DOM manipulations can cause performance issues in larger applications.

Angular: In contrast, Angular supports unidirectional data flow and one-way data binding. It uses a more efficient change detection mechanism that significantly reduces the number of updates required and increases the overall performance of the application. Additionally, Angular provides Ahead-of-Time (AOT) compilation, which converts Angular HTML and TypeScript code into efficient JavaScript code before the browser loads it, thus increasing performance even more.

Mobile support

AngularJS: AngularJS was primarily designed for desktop applications, limiting the mobile development support. This limitation can be a challenge in today's mobile-first world.

Angular: Angular, however, was built with mobile support in mind, which allows for creating responsive and performant mobile apps. Angular's component-based architecture together with its efficient rendering and change detection mechanisms makes it the preferred language for mobile development.

Dependency injection

AngularJS: AngularJS has a simpler, less flexible dependency injection (DI) system, which can sometimes lead to challenges in managing dependencies in larger applications.

Angular: The DI system in Angular is both more advanced and modular, therefore, it enables better organization and reusability of services and components. Developers can design more testable and maintainable code using this DI system. Moreover, because it is simpler to inject services into components or other services, Angular’s hierarchical injector system helps manage dependencies better.

Modules

AngularJS: With AngularJS monolithic approach, the entire application is typically bundled together. This approach can lead to issues in managing large codebases, as the application grows in size and complexity.

Angular: Angular development inlcudes NgModules, which support modular development. The use of NgModules enables the developer to break the application into modular, functional parts that can be built and tested separately. As a result, this modularity allows for lazy loading (when the application is loaded on demand), reducing start-up time and increasing performance.

When to consider the AngularJS to Angular migration?

Migrating from AngularJS to Angular can greatly benefit both your technology stack and business operations. There are some situations under which it is particularly advantageous to make this shift:

1. Pursuing long-term technological and business benefits

• Moving on from AngularJS in 2021: With AngularJS deprecating, shifting to Angular is inevitable. Angular has Long-Term Support (LTS) from Google with new updates coming every six months, hence your application will always be responsive for its users over a longer period. This transition also allows for ongoing adaptability to new requirements without necessarily starting all over again.
• Dealing with scalability issues: Angular features modular architecture that would help scale out if your current system has become unmanageable. Angular employs reusable and independent data components that facilitate fast and orderly growth of a system.

2. Enhancing technical performance

• Improving user experience affected by performance problems: Angular boosts application’s speed and reliability through Progressive Web Apps (PWAs) and Ahead-of-Time (AOT) compilation, thus enhancing user experience in terms of quickness and intuitive interaction.
• Mitigating performance bottlenecks and unexpected errors: Angular has the potential to greatly boost application performance. Utilizing Web Workers for background processing and server-side rendering enhances page load speeds. Additionally, TypeScript's early error detection contributes to higher development quality by catching issues before they escalate.

3. Reducing technological expenses

• Reducing dependence on paid third-party tools: Angular includes a comprehensive suite of built-in tools, such as the Command Line Interface (CLI) and Integrated Development Environment (IDE). These tools streamline the development process and reduce the need for expensive third-party software.
• Optimizing resource use by avoiding rebuilding from scratch: Angular Material UI offers a pre-designed kit that allows for rapid, user-centric design implementation. Incorporating separated modules instead of starting from scratch, developers can deliver polished products more efficiently.

“Upgrading from AngularJS to Angular is a development option that allow your application to remain modern, grow in scope and performance, while also optimizing business costs and resources. If your goals include long-term technological and business advancements, performance optimization, and cost efficiency, then such an upgrade will do you right.”

Andrei Zhukouski

Chief Strategy Officer

Preparation and setting up the upgrade plan

Shifting from AngularJS to a modern version of Angular is a major job that calls for serious preparation and planning, as this process can impact service delivery, especially for critical business applications. 

A sound migration plan will help ensure the success of this transition. The following steps outline the key aspects of preparing for and setting up your migration plan.

1. Assess the current application

• Determine which parts of your application are most essential to correctly prioritize the migration tasks. Identify critical components, services, and directives that need to be migrated first.
• Conduct a thorough assessment of your existing AngularJS application to understand its structure, dependencies, and overall size. This will help you identify the scope of the migration and any potential challenges.

2. Create a migration plan

• Come up with a comprehensive migration plan that includes a detailed timeline, resource allocation, and the steps required for the migration. Based on this plan, assign responsibilities to team members and set realistic deadlines.
• Make sure that your plan includes time for testing and validation, so as to maintain the application uptime and functionality during the migration process.

3. Set up TypeScript.

• Use the @types/angular package, which ensures that your existing JavaScript code and TypeScript can interoperate. This package provides type definitions for AngularJS, allowing you to gradually introduce TypeScript into your project.
• Integrate TypeScript modules and use the TypeScript Compiler to achieve seamless integration between AngularJS and TypeScript. This will help you catch potential errors early and improve code quality.

4. Use the ngUpgrade toolkit to enable coexistence of both frameworks.

• The ngUpgrade toolkit allows AngularJS and Angular to coexist in the same application, enabling you to incrementally migrate components and services.
• This toolkit simplifies the migration process by allowing you to operate with AngularJS and Angular simultaneously, reducing the risk of disruptions.

5. Transfer services and components.

• Use the downgrade components feature to make Angular components available within the AngularJS part of your project. This enables you to start using Angular components without waiting for the entire migration to complete.
• Make sure every part of your code is compatible with the newest Angular version by revising some specific sections. If needed, adjust existing AngularJS services and components in a manner that aligns with the latest Angular’s recommendations.

6. Utilize UI-Router to ensure efficient navigation.

• Use ngUpgrade to support routing seamlessly by default, facilitating a trouble-free transition.
• Consider utilizing the UI-Router to ensure efficient navigation and migration of your application’s routes. This will help maintain a consistent user experience during the migration process.

How to migrate AngularJS to Angular, step by step

Migrating an AngularJS application to the latest version of Angular involves several key steps. Below is an outline of the process we follow to ensure a successful transition.

This guide provides a general framework for migration. Each project has its unique environment, input data, and constraints, so we tailor the process to meet your specific requirements.

Set up Angular environment

1. Update Node.js and npm: Ensure you have the latest stable versions of Node.js and npm installed.

2. Install the Angular CLI globally using:

3. Create a new Angular project using the Angular CLI:

Run the AngularJS and Angular side by side.

1. Set up hybrid environment. Install necessary dependencies for running AngularJS and Angular together:

2. Bootstrap AngularJS and Angular together. Modify main.ts to bootstrap both frameworks:

Migrate components

1. Identify components to migrate:

• Start with simple, reusable components.
• Migrate one component at a time to avoid breaking changes.

2. Migrate the component. 

• Create the Angular component using Angular CLI:

• Copy the HTML, CSS, and logic from the AngularJS component to the Angular component.
• Downgrade the Angular component to use it in AngularJS:

Migrate services

1. Identify services to migrate:

• Start with standalone services that have minimal dependencies.

2. Migrate the service.

• Create the Angular service:

• Copy the logic from the AngularJS service to the Angular service.
• Downgrade the Angular service to use it in AngularJS:

Migrate routing

1. Set up Angular routing: Define routes in Angular using RouterModule in app-routing.module.ts.

2. Gradually migrate routes:some text

• Migrate routes one by one from AngularJS to Angular.
• Use ngRoute in AngularJS and RouterModule in Angular for handling routes during the transition.

Migrate directives and pipes

1. Migrate directives:

• Create Angular directives to replace AngularJS directives.
• Downgrade the new Angular directives for use in AngularJS.

2. Migrate filters to pipes: Create Angular pipes to replace AngularJS filters.

Conduct testing

1. Unit testing: Write unit tests for each migrated component, service, and directive using Jasmine and Karma.

2. Integration testing: Perform integration tests to ensure that AngularJS and Angular components work together seamlessly.

3. End-to-end testing: Use Protractor for end-to-end testing to verify the application's functionality from a user perspective.

Clean up and finally migrate

1. Remove AngularJS dependencies: Once all components, services, and routes are migrated, remove AngularJS dependencies.

2. Finalize bootstrap: Update main.ts to bootstrap the Angular application only.

3. Refactor and optimize:some text

• Refactor the Angular application for better performance and maintainability.
• Optimize the application by following Angular best practices.

Deploy

1. Build the application: Build the Angular application using the Angular CLI:

2. Deploy to production: Deploy the built application to the production server.

Challenges and solutions in migrating large applications from AngularJS to Angular

Migrating a large application from AngularJS to Angular can be a difficult process. However, addressing common challenges with effective solutions can ensure a smooth transition. Here are some of the primary challenges and their corresponding solutions:

1. Complexity of the existing codebase

Challenge: Moving a codebase with multiple dependencies and custom directives to the component-based architecture of Angular might seem like a huge mountain.

Solution: First, carry out a detailed audit of the already existing codebase in order to determine the main components, services, and dependencies. Employ Angular’s upgrade tools and techniques including ngUpgrade to enable its concurrent operation with AngularJS. Refactor and replace AngularJS component with Angular equivalents in each section successively until all are done, thus managing complexity.

2. Handling state management

Challenge: If your application uses custom solutions or libraries, migrating the state management logic can be tricky. It is because AngularJS and Angular handle state management differently.

Solution: Use Angular’s built-in state management tools and patterns for more complex state management needs. Such tools include Angular services or NgRx. First, map out the existing state management approach in AngularJS and then adapt it to Angular's approach, testing adequately so that consistency and correctness remains maintained.

3. Differences in dependency injection

Challenge: Migrating services and components can be complicated due to different dependency injection systems used by AngularJS and Angular.

Solution: Update AngularJS services to leverage Angular's dependency injection system, which is more sophisticated and modular. The use of Angular’s hierarchical injectors together with its Dependency Injection (DI) framework is essential to better handle service dependencies and guarantee seamless integration.

4. Performance optimization

Challenge: Taking into account that performance optimizations in AngularJS may differ from those in Angular, ensuring that the migrated application performs well is obligatory.

Solution: Take advantage of Angular’s performance optimization features, such as Ahead-of-Time (AOT) compilation, tree shaking, and lazy loading. Employ the Change Detection mechanism and monitor performance using various Angular DevTools to locate and fix any performance issues that may exist.

5. Training and skill gaps

Challenge: Developers accustomed to AngularJS might need training to become proficient with Angular's new features and TypeScript.

Solution: Invest in training and upskilling your development team. Give access to Angular tutorials, workshops, and documentation to help them get up to speed. Foster a culture of knowledge sharing within the team by encouraging practices like pair programming.

6. Testing and quality assurance

Challenge: Maintaining the application’s quality and reliability after the transition can be difficult, particularly when there has been a lot of code change.

Solution: Create a complete testing strategy that comprises unit tests, integration tests and end-to-end tests. Use Angular’s Jasmine and Karma testing tools to write and run tests. Implement CI/CD pipelines to automate testing and catch errors early.

Consider TYMIQ as your migration partner

As AngularJS becomes outdated, the advantages of Angular make the transition fully justified. The only thing that matters is not whether to migrate or not, but rather when and how the process should be initiated. Converting AngularJS to Angular is critical if you want your application to perform better, run faster, and allow for easier feature implementation.

TYMIQ provides smooth AngularJS to Angular migration services to respond to your transition challenges. We use a systematic method to transition your applications to the latest Angular framework, maintain hybrid codebases, and progressively refactor components to ensure minimal disruption. 

Contact TYMIQ for assistance in moving from AngularJS to Angular, thus ensuring your application stays ahead with the latest technology advancements.

FAQ

Why migrate from AngularJS to Angular? 

With the closure of AngularJS announced in 2021, the migration becomes essential for longevity. Angular, backed by Google’s Long-Term Support (LTS) and updated biannually, ensures lasting functionality and relevance. Moreover, Angular’s reusable, modular components make it easier to scale your application as your business grows. For more migration reasons, read on here.

What is the difference between Angular and AngularJS? 

AngularJS and Angular differ significantly in their architecture, language, performance, mobile support, dependency injection, and modularity. For the details on each parameter, read on here.

What are the most common methods of AngularJS to Angular migration? 

There are two most common migration scenarios: 

1. Angular app development from scratch - A complete rebuild of the application, ideal for outdated codebases and projects with sufficient resources. Optimizes application structure and eliminates obsolete code, but requires significant time, resources, and may disrupt ongoing operations.
2. Incremental transition - A gradual migration approach, suitable for large, complex applications that require minimal downtime. Supports hybrid environments, reducing risks through phased updates, but may extend migration timelines and require managing two frameworks simultaneously.