AngularJS Migration Guide: Answers from the Experts | ModLogix

8 min readSep 30, 2021

The upcoming AngularJS end of life leaves no choice for organizations but to think over migrating to more reliable frameworks. But the closer the depreciation date is, the more questions and concerns around the migration arise. Some business owners are terrified by the possibility of needing to rewrite the app, while the rest of them just got used to good old AngularJS code and structure.

However, December 2021 is the AngularJS end-of-life date. After this time, the apps will be exposed to security vulnerabilities that are critical for businesses and users. To help companies get into the migration path, we asked industry experts about AngularJS and its peculiarities.

In this AngularJS migration guide, we gathered valuable insights from developers and thought leaders who already abandoned AngularJS in favor of modern tools. Where should you start the upgrade? What processes must you automate? Read these 10 questions and answers that dispel your doubts.

Is rewriting everything from scratch the only option to upgrade from AngularJS?

This burning question baffles organizations that own AngularJS apps around the world. Rewrite or resort to other approaches? Where’s the “the golden mean”?

Previously, we uncovered 3 typical approaches to move from AngularJS to Angular: rewrite, hybrid with ngUpgrade, and Angular Elements. In short, a hybrid with ngUpgrade option implies running both frameworks simultaneously. Angular Elements package, in turn, allows automatic transforming Angular elements into custom ones. Both approaches facilitate migration but, in the meantime, they aren’t suitable for most of the legacy solutions.

9 out of 11 experts said that the only way to update in AngularJS is to create the whole app from scratch in some new framework or resort to a gradual upgrade. The thing is, most apps inherited tangled architecture with plenty of controllers used instead of components. Most likely, you’ll spend more effort on streamlining the existing codebase.

Our expertise also shows that it’s better to redesign a system because of fundamental differences in the syntax and structure of modern tools.

Pros of rewriting:

opportunity to resolve performance and inconsistent code issues;
add and expand the functionality of existing solutions;
revise the business process and its efficiency;
save costs on future maintenance and recruitment.

Cons of rewriting:

lengthy and expensive procedure;
overall complexity, incl data loss, errors, etc.

The verdict is quite clear — the successful migration involves rewriting almost everything from scratch. However, despite the complexity, the rewriting efforts will pay off shortly.

Is there any difference in frameworks to migrate to? What to choose: Angular, Vue or React?

The reasonable question before the migration from AngularJS would be the new framework. Today, the technology market has a wide choice of front-end tools headed by 3 leaders: Angular, React, and Vue.JS. Based on the Stack Overflow and GitHub surveys, each tool generates an equal amount of interest from developers. But what do they offer in practice?

Angular

Angular, the obvious successor of AngularJS, was released in 2009 by the Angular Team at Google. Despite the common roots, these frameworks are utterly different. Angular uses a more consistent language (TypeScript) and has a component-based architecture that is better structured.

When it comes to migration from AngularJS to Angular, you can automate some of the processes, but basically, everything must be redesigned. Angular is widely used for large-scale enterprise projects because of the full-fledged package of solutions such as navigation features, advanced refactoring, etc.

At ModLogix, we’ve worked on a couple of successful AngularJS to Angular migration projects. We’ve collected the best approaches, hacks, and tips in our ultimate AngularJS to Angular migration guide.

React

React, developed by Facebook, has gained a lot of popularity in recent years. It has broad community support, solid feature set, documentation and generally has little to no difference from Angular or Vue. React is equally used for small, medium, and enterprise-level applications which makes it a decent choice for any project.

If everything is so crystal clear, are there any issues when migrating from AngularJS to React? The scheme is almost identical to Angular, as you must fully recreate the app. Developers rewrite the legacy components in React using top-down or bottom-up approaches.

Vue

Vue is another JavaScript library driven entirely by the open-source community. Unlike its competitors, Vue offers highly customizable features to build any sort of app. Developers appreciate it for its simplicity and flexibility, even though such freedom can result in poor coding.

If you decide to migrate AngularJS to Vue.js, you won’t stand alone on this path. Their official community offers extensive support backed up by helpful examples in Stack Overflow and GitHub repositories.

To sum up, there is no distinct difference in the frameworks you’ll choose to replace AngularJS. The things you should consider are your business and migration goals and current tech stack. After all, you can always consult with experienced vendors to find the most natural fit for your case.

Will your AngularJS app suffer from security vulnerabilities after 2021?

According to our experts, security vulnerabilities in legacy AngularJS code are the most solid reason for migration. Official announcements state that security patches and regular updates won’t be distributed anymore, which means possible security loopholes in your app.

Curiously, AngularJS has always been a stable framework that’s proven by statistics — it hasn’t experienced any vulnerabilities in 2021. But what might happen without constant improvements and community activity?

The app becomes incompatible with dependent components such as jQuery. Consequently, with each jQuery update, the outdated AngularJS system may crash or work improperly.
Browser compatibility becomes questionable as well.
You need to address unforeseen issues that can arise in AngularJS by yourself.

What can you leave as is during the upgrading?

Upgrading the AngularJS app as a part of the migration process means doing everything from scratch. But the part you must preserve is the business rules that describe relationships between objects. Simply put, business logic must be strictly mirrored in the target system. Such a strategy gives you a full understanding of how the new system will work.

“Except for some code workflow (would not say even code), rest has to be completely rewritten. Why I said code workflow due to the change of programming from JS to TS, and it has to be at an advanced level where you have to put code in a well-structured manner to make it perfect.”
Mukul J., Software Engineering Manager at Intel
“Maybe should be considered save only logical and structural business rules, all other written code put in trash and re-write from 0 point.”
Daniel Krug, Software Engineer

Just to be clear, the upgrading process breaks down into cohesive steps:

1. Planning the migration (streamline AngularJS code to follow guidelines, gather the documentation, refactor code pieces, etc.)

2. Choosing a migration approach: top-down (upgrading separate features or screens) or bottom-up approach (working with individual components)

3. Supporting existing version and creating the new one in parallel

4. Running auto-tests

5. Setting up Continuous Integration/Continuous Delivery (СI/CD) for the sake of productivity

Why migrate from AngularJS to Angular?

Numerous companies still use AngularJS to build web interfaces, and an impressive number of developers openly dislike it. According to the 2021 Stack Overflow survey, 76.82% of developers are dreaded by AngularJS.

Critical flaws of AngularJS that must be considered:

AngularJS has a two-way data-bind feature that leads to delays and bottlenecks during the development. As a result, poor performance and maintainability. In further Angular versions, the community improved this model a lot to avoid the app’s overload. It allowed companies to enhance overall app performance and operation speed along the way.
AngularJS can’t provide the feature set to build accessible and user-friendly websites. Conversely, modern tools use Material design templates, introduced by the Google development team, to create up-to-date design solutions.

“One of the reasons why organizations must move from AngularJS to Angular to satisfy new age demands is because of the enhanced user interface provided by material design.”
Dusan Stana, Founder & CEO of VSS Monitoring

Much has been said and written about the AngularJS architecture, Model View Controller (MVC) pattern. Compared to Angular component-based architecture, MVC complicates the software development process and stirs up the development time.

What are the compelling arguments for companies to stay with AngularJS?

The Angular team confirms that “ all AngularJS applications that work now will continue to work in the future.” So, there’s every hope of continuing to use a familiar system for a lifetime, isn’t it?

Partially, it’s true, and there are several conditions that may justify the use of the AngularJS app for business purposes after 2021:

The system will be retired shortly.
The system must be maintained only. It involves fixing critical bugs and serious flaws but not developing new features or improving software state on a large scale.
AngularJS features are vital for the current app. For example, the basic functionality is fully dependent on third-party tools that aren’t available in Angular (WebStorm and IDE).
You are not using AngularJS as a Single-page application (SPA).

Summarizing these points, experts agree on one argument - if the app is going to be replaced anyway and you are ready to take involved risks, keep staying on the final AngularJS version and rely on package managers.

What are the best practices for upgrading AngularJS to Angular?

As we mentioned previously, loads of companies and developers are reluctant to start the modernization of outdated AngularJS apps. Despite the challenges, there’s also good news — migration from AngularJS to Angular is already well-defined.

The Angular community provides official documentation on how to migrate from AngularJS to Angular. Also, their GitHub forum is plastered with useful tips and insights on migration.

Our team and industry experts created our own roadmap for migration based on real-life experience.

Tip 1. Invent the apps that should be migrated. By knowing the true state of the system, it would be easier to estimate the process accurately and avoid extra expenses.

Tip 2. Decide on the strategy you’ll follow: top-down or bottom-up. You may focus on upgrading concrete elements or components as a whole; the one thing is it must comply with your business rules.

Tip 3. Clean the current codebase in conformance with the AngularJS Style Guide. The more structured the app is, the easier it will be to migrate it via auxiliary tools.

Tip 4. Consider a hybrid model to handle routing. Angular has an updated routing feature that does not work for AngularJS. When migrating big enterprise systems, move one route at a time and run two instances of the app simultaneously.

Tip 5. Get rid of $rootScope and $compile that are not available in Angular. The fewer dependencies on $scope, the better. They can be hidden in such functions as $compileProvider.preAssignBindingsEnabled(true), $element.replaceWith() and services that are used to store currently global variables.

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Originally published at https://modlogix.com on September 30, 2021.