How to Migrate AngularJS to Angular
13 min.

So, you’ve decided to opt for modern, future-proof technologies and migrate AngularJS to Angular. It may have been a tough decision as the transition poses challenges such as potential solution shutdown until the release of the new version, feature and API migration, and embracing the architecture of the newer technology.

We at ProCoders know exactly what you’re about to go through as we’ve updated multiple projects in the 9 years of our experience. As a matter of fact, our developers can move your software without having to shut it down!

Sorry, that was a spoiler…

In this guide, we talk about migration approaches, updating framework versions, and how to migrate AngularJS to Angular step by step. Have no time to read an article? We have a short video with the main points for you to learn here :point_down: Enjoy!

Which Approach in AngularJS to Angular Migration to Choose?

Rewrite ProcessGradual, module-by-moduleComplete rewrite
Code CoexistenceOld and new code coexistOnly old code functions
Feature DevelopmentFeatures developed in both projectsNew features developed in new code
Suitable Project SizeLarge projectsMedium to smaller projects
Timeframe for RewriteExtended periodShorter timeframe (2-3 months)
Development Team SizeSmall development teamLarger team for a dedicated period
Old Functionality During RewriteContinues functioningFunctionality is frozen
Support Costs for Old SolutionHigherN/A
Architecture ChangesComplex maintenance of hybrid architectureClean architecture and new design introduction
Additional Development OverheadYesN/A

“Q: Is migrating from AngularJS to Angular as simple as upgrading dependencies? 

A: Nope, it’s not a walk in the park. While they might sound alike, it’s more like trying to turn a tricycle into a spaceship – they’re just not built the same way.”

Oleg Kopachovets, ProCoders CEO

After you study why migrate from AngularJS to Angular and make the decision, you need a well-thought upgrade plan. In our experience, some applications could only be rewritten from scratch, while others only required an update. Here are some approaches and factors leading to them that we usually discuss when setting up an AngularJS to Angular migration plan.

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This is a complete rewrite with only the old project functioning while transitioning to new code. The development of features in the old project is frozen. This approach is suitable for medium to smaller projects that can be rewritten within an acceptable business timeframe (e.g., 2-3 months). 

Existing functionality is frozen during development, and new features are created in the new code. The shorter timeframe can be achieved by adding a large number of developers for a dedicated period. The AngularJS to Angular migration benefits of revolution include a clean architecture, more freedom in terms of features, and the ability to introduce a new design.

Legacy applications often need rewriting because they are so out of date that migration can be a serious hassle unless an entirely new code is developed. 

When planning how to migrate from AngularJS to Angular, consider that rewriting offers more flexibility but may be costlier since the code reusability of the initial app can be low to none.

Revolution Angular


“Q: What’s the second approach to migration? 

A: Ah, that’s the modular approach. Picture this: you’re building a new skyscraper next to an old one, and they need to coexist peacefully. You can achieve this with “ngUpgrade” and “UpgradeModule.” It’s like renovating a house while you’re still living in it. We did it for the MultiQ project, and it worked like a charm!”

Oleg Kopachovets, ProCoders CEO

This is a gradual, module-by-module rewrite. New and old code coexist simultaneously (thanks to ngUpdate). Features developed in both projects. Suitable for large projects where rewriting all at once isn’t feasible within a business-friendly timeframe. Requires an extended period and a small development team. Drawbacks include support costs for the old solution, complexities in maintaining a hybrid architecture, and additional development overhead.

Evolution is best suited for large, complex applications which are quite time, money, and labor-consuming. An update is quicker to release in this case. 

Pro tip: Use a hybrid approach, where various parts are gradually rewritten until you have
      a fully successful upgrade. Although this hybrid code is more difficult to maintain,
      it’s a common practice at ProCoders due to the convenience of the result for our

      That is, at no point in the process do you have two parallel applications. Instead,
      the new and the old code coexist until the update process is complete.

ProCoders’ CEO Advice

For this guide, we’ve decided to go further and ask our own CEO, Oleg Kopachovets, for some tips on Angular migration. Here are the outtakes and main quotes:

  • Sometimes an upgrade from AngularJS service to an Angular project may take even more time than building a new app from scratch. That’s because your team may need to reverse-engineer a lot of details.
  • When estimating the time required for upgrading, consider the timeframe for the AngularJS app, expecting to spend at least half that time for the transition.

“Q: Can you estimate the time needed for migration? 

A: Estimating migration time is like predicting the weather; it’s tricky. But think of it this way, if they spent over 1,000 hours on the old app, you can’t expect it to transform into a new app in less than 500 hours (or three months)”

  • Prioritize research, unit tests, and preparation for a smooth transition, acknowledging the opportunity to refresh the UI without making drastic changes that could deter existing users.

“Q: What’s the importance of a thorough research phase? 

A: Think of the research phase as the treasure hunt before a pirate ship adventure. You’re making sure there are no hidden traps (bugs) in the old map (code) that will haunt your new journey.”

  • During the upgrade process, it is possible to incorporate both frameworks without having to shut down the application for months by using:
    • The “ngUpgrade” library for gradual migration without rewriting the entire application
    • The “UpgradeModule” class as one of the utilities for bootstrapping and communication between AngularJS to Angular modules
    • The “downgradeModule” function to integrate the newer components into a JS app
    • The “upgrade/static” function to do the opposite
  • There’s no super-smart converter that will transform the old software into a neat architecture-specific one. However:

“Yep, there are tools like “ngUpdate” and “ngMigration-Assistant.” Plus, you can call in the AI squad – tools like Github Copilot and ChatGPT can help rewrite code snippets, saving you a cool 25-30% of your time.”

If you need to move a template, a converter may work fine. However, for a professional, effective, and issue-proof transition, it’s necessary to hire web developers with experience in the field.

How to Migrate AngularJS to Angular: Step-by-Step Guide from ProCoders

So, how exactly should you approach moving the solution to avoid data loss and maintain the features? ProCoders professionals have gathered to create an AngularJS to Angular migration project step-by-step for you to get familiar with the process. 

Keep in mind this section is NOT the final algorithm we use. Each project is unique, so we always research the details, study your needs and requirements, and then come up with the most optimal decision.

Step 1: Prepare by setting up TypeScript using the @types/angular package. Then, use the TS Compiler and a TS module integration to make the language interoperable with the old JavaScript code.

Step 2: Create a new build of the existing AngularJS app using Angular CLI. Some developers use Webpack directly instead but, in our experience, that’s time-consuming, especially since CLI supports Webpack internally. Copy the AngularJS files to a new folder in Angular. 

Step 3: Use the ngUpgrade toolkit to implement a hybrid update and operate two frameworks simultaneously. Utilizing default function parameters will help you ensure backward compatibility and optimize code. This makes the migration process invisible to the users and more convenient for the client.

Step 4: Transfer services and component APIs. You can use the downgrade AngularJS to Angular components to make the newer parts to be available within the AngularJS segment of the project. You might need to rewrite some code while migrating the AngularJS component to the new version of the app. One crucial step is to refactor and adapt the AngularJS module configuration files to align with the updated folder structure and configuration requirements of Angular.

Step 5: At the final stages comes routing, often implemented using UI-Router. ngUpgrade supports this by default, and UI-Router has smooth support for hybrid migration.

Step 6: Due to differences in the JS and Angular template syntax, you may encounter compile-time errors, so make sure to test the app after the migration. Check if all parts of the solution align with the new Angular architecture.

After all the checks and refactoring of AngularJS dependencies, factory(ies) that are substituted with services in Angular, and thorough testing, all you have to do is to update to the most stable versions of the framework when necessary.

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How to Update Angular Versions

The Angular framework is constantly updated, there are new versions almost every year, and updating to the latest version is always a good thing due to bug fixes and new features.

Pro tip: Make sure the version you want to update to is stable. The official website of the framework will update you on all new releases, patches, support, etc.

The official steps of how to update your framework version are:

  • Running the ng update command, given the update is simple. The results will show you new availability, along with steps to perform to install them.

Pro tip: If you need to jump several major versions, it’s better to do it one at a time. For example, in case you want to upgrade from version 10 to 14, it’s better to get to 11 first, then 12, and so on.

That is all! See how easy it is! Our programmers have many more tips and tricks on moving from AngularJS to Angular and updating the versions of the latter. All you have to do is contact us!

Angular Versions

Useful Tools for the Migration to Go Smoothly

Ensuring a smooth migration from AngularJS to Angular involves more than just a plan; it requires a set of practical tools to assist in the process. Let’s explore some of the essential tools that can make this transition journey more manageable:

  • cloc (Count Lines of Code): This command-line tool swiftly calculates the number of lines of code in your project, categorizing them by programming languages. It offers an initial glimpse into the size of your codebase, a crucial starting point.
  • ngMigration Assistant: Developed by the Angular team, this tool analyzes your AngularJS project and provides migration recommendations. It offers an assessment of the potential complexity of your specific migration, helping you understand what lies ahead.
  • Plato or escomplex: These tools provide metrics for JavaScript code complexity. They can help you gauge how intricate particular sections of your application are and identify potential trouble spots. Understanding code complexity is important for effective refactoring.
  • ng-inspect: This browser extension for Chrome and Firefox simplifies the visual analysis of AngularJS applications. It allows you to quickly identify which controllers, directives, and services are used on different pages of your app, aiding in the understanding of its structure.
  • Dependency Graph Tools: Tools like ‘madge’ can be invaluable for analyzing dependencies within your application. Understanding your application’s dependency structure can help determine which modules or components are most closely linked. This insight helps you pinpoint where to start the migration process, often beginning with less interconnected modules or files.
  • AI/GPT Tools: Utilize AI-powered tools like ChatGPT or Claude2, especially the latter. You can feed them class or dependency diagrams and request recommendations. Additionally, you can provide your ‘packages.json’ file to identify outdated libraries, streamlining the update process.

By using these practical tools, you’ll be better equipped to tackle the complexities of migrating from AngularJS to Angular, ensuring a more efficient and successful transition.


ProCoders Case Study: Real-world AngularJS to Angular Migration

Here at ProCoders, we’ve helped numerous clients convert AngularJS to Angular. We actually have experts in our pool who are well-versed in AngularJS, which is a rare thing. We have multiple cases with migration, including our Ushahidi and MultiQ. Today, we want to share a part of our interview with one of the most experienced ProCoders developers about MultiQ – a digital signage provider.

Q: What did you do to make the transition smooth?

Andrew: I used a HybridHelper while migrating; the solution allowed both frameworks to function simultaneously so the project was up and running while the developers were working on the migration. I also implemented the Upgrade and Downgrade components that help run AngularJS sections on the newer framework and vice versa.

Q: How did you come to use a HybridHelper and Upgrade and Downgrade components in your approach?

Andrew: The client had already heard about these solutions but had doubts before consulting with me. I reassured them this approach would speed up the process and make it easier tenfold.

Q: How much time did it take?

Andrew: It took around a year to rewrite all the necessary components while the project was live and the client was producing revenue. The migration process itself took a month or so, whereas the original project was completed in 5 years! 

Q: What were the complications and obstacles along the way?

Andrew: There are not many AngularJS to Angular migration challenges, but there is one huge pain – scope. In AngularJS, the scope is an object that acts as a bridge between the view (what users see) and the controller (the logic behind it). Since Angular uses a component-based architecture with properties and event bindings instead of scope, the migration process involves refactoring the code to align with the new structure.

Q: How many specialists were working on the project?

Andrew: Only two. Me and Miroslav (a Senior Angular developer at ProCoders) were on the team. Our team’s big advantage is having Senior experts who know the ins and outs of not just the modern frameworks but the outdated ones as well.

The two of us have done what a team of 5-6 less experienced developers would do in the same timeframe.

Q: What was one of the best results for the client?

Andrew: Aside from getting an updated, future-proof solution, our partners at MultiQ were in business the whole time as we didn’t need to close the old resource. This approach has probably saved the client hundreds of thousands of dollars!

So, having a software development partner with experience in these frameworks is a must. But how to find a decent company to provide or augment your Angular team?

Ensure a Seamless Transition from AngularJS to Angular with a Committed Software Development Partner.

How to Choose the Right Development Partner for Migration or Make Suitable In-House Team Extension

There are multiple ways to hire Angular developers, but you need high expertise in the field, which is harder to find. Experience is necessary when deciding whether it’s better to migrate or write an app from scratch, which AngularJS components to rewrite, what utilities to use to make the process quick and smooth, etc.

Here are some things we at ProCoders recommend paying attention to:

  • Go through case studies and reviews – you can use sites like Clutch, Upwork, etc. On top of that, if there is a way to contact current or previous customers and find out what they think about the potential partner, that would be an advantage too. 
  • Sign official documentation (NDA, contract, etc.) – this will help you maintain the integrity of your project. 
  • Pay attention to the time zone – communication is key during the upgrading process. We at ProCoders always look for ways to maintain continuous communication between clients and developers. We’ve achieved a less-than-30-minute response time during working hours.
  • Developer qualifications – the devs must be familiar with both frameworks and well-versed in the techniques used while upgrading from AngularJs to Angular. 
  • Interview the developers – we at ProCoders always favor our partners interviewing the programmers they will work with. Such an approach sets the tone for collaboration and liberates clients from worries about working with us (if there are still any, which is rare).

    One of the first questions you must ask the dev is what method they would use during the process. How was their performance rated during their previous migrations? What problems did they face?
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Is it possible to migrate AngularJS to Angular?

Yes, it is possible to migrate AngularJS to Angular. The process involves a gradual upgrade using tools like ngUpgrade to allow both frameworks to coexist during the transition.

Can I use AngularJS in Angular?

Yes, you can use AngularJS within an Angular application during the migration process by using the ngUpgrade library, which allows you to run both frameworks simultaneously.

What is the difference between AngularJS and Angular?

AngularJS is the original version, based on JavaScript, while Angular (often referred to as Angular 2+ or simply Angular) is a complete rewrite in TypeScript with improved performance, modularity, and scalability.

Why AngularJS is replaced by Angular?

AngularJS was replaced by Angular to address performance issues, provide better modularity, and offer a more modern development approach with TypeScript, resulting in a more efficient and scalable framework.

Which is in demand Angular or AngularJS?

Angular is in higher demand compared to AngularJS. Modern projects prefer Angular due to its advanced features, better performance, and active community support.

What are the key differences between AngularJS and Angular?

AngularJS uses JavaScript, while Angular uses TypeScript. AngularJS follows an MVC-based architecture, whereas Angular uses a component-based architecture. Angular offers better performance with Ahead-of-Time (AOT) compilation and has a more robust CLI and modern development tools.

Why should I migrate from AngularJS to Angular?

Migrating to Angular provides improved performance, better maintainability, access to modern features, enhanced AngularJS to Angular security, and a more active support community.

What are the main steps in migrating from AngularJS to Angular?

The main steps include analyzing your current AngularJS application, setting up the Angular framework alongside AngularJS using ngUpgrade, migrating AngularJS to Angular services services and components incrementally, testing each step thoroughly, and fully transitioning to Angular and removing AngularJS dependencies.

How do I prepare my AngularJS application for migration?

Preparation involves updating AngularJS to the latest version, cleaning up the codebase and removing deprecated features, ensuring comprehensive test coverage, and planning the migration strategy by breaking down the process into manageable phases.

What tools can assist with the migration from AngularJS to Angular?

Tools like ngUpgrade, Angular CLI, and TypeScript can assist in the migration. Additionally, using automated migration tools and following official migration guides can streamline the process.

What are the AngularJS to Angular migration best practices?

Best practices include incrementally upgrading services and components, using Angular services in AngularJS code during the transition, keeping services stateless and decoupled, and thoroughly testing each migrated service.

What resources are available to help with the AngularJS to Angular migration process?

Resources include official Angular documentation and migration guides, community forums and blogs, tutorials and courses on platforms like Udemy and Pluralsight, and consulting with experienced Angular developers or companies specializing in migrations.


At ProCoders, we’ve gathered years of experience with the sole purpose of helping our partners grow and transition to modern technologies. We know that making a decision to upgrade AngularJS to Angular can be challenging, so we’re ready to assist.

We’ll choose the right way to upgrade your software through migration or by rewriting it from scratch. Our specialists will consider your time and budget plans, using their experience to have an optimal solution for you as we have our second call. 

Our developers, experienced in both frameworks, will handle your app carefully, migrating while it’s still in operation, providing service to customers and making you money.

If there’s ever a perfect time to slow down and consider moving to newer future-proof technologies, it’s now.

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