Working with legacy apps

Angular 9 has just been released, over the last few years, Angular has gone from version 2 to 9 its growth is amazing, and with each release, there are new features and new ways of working with Angular.

While this is great and shows that Angular is still a vibrant framework, it does mean that having a long term Angular app needs to be closely maintained. Version numbers need to up upgraded, test coverage needs to be maintained, there is a lot of work involved in managing legacy Angular apps.

What is a legacy app?

For me, a legacy app is one that cannot be easily maintained. Where the code base is structured in such a way that it takes a new developer on the project a few weeks to feel comfortable in being able to add new features to the app. Where the application structure doesn’t follow any industry standards and where it takes a series of steps to just get the app running locally.

With applications like this, not being able to add new features or upgrade the underlying technology that is running them means that eventually, the client will begin to resent the application that use to make their work so much easier. They become a drain on the clients time where they have to find ways around the problems the old legacy application is giving them.

How can legacy apps be improved

Not all is lost with legacy apps, there are ways to bring them back to what they were. It just takes time, effort and clear understanding with the client that things may seem to get worse for a short while but soon the application they use every day will be better.

What steps can a team take to update a legacy Angular application?

The steps that a team can take when upgrading a legacy Angular application, they are:

  1. Have Unit Tests – tests help by making sure any code changes have not broken other parts of the application. As the code is upgraded, or versions of packages are updated tests can be run to show these changes have not had adverse effects on other parts of the app.
  2. Have UI tests – these tests can be used to show how the app works for the end-user. Even if you have a legacy app that doesn’t have any end to end tests, tools like Cypress are so powerful now, it makes writing end to end tests easier. Having tests like this in place before making changes to a legacy app is a good idea so these tests can be run to check that the app still works as it did before.
  3. Use Angular Elements to upgrade an app in stages – if you have an AngularJS application that can’t be re-written in one large go. Angular Elements are a great way to improve parts of an application in stages. Angular Elements are complete Angular (not AngularJS) applications that can run within AngularJS application (this is a method I used to upgrade parts of a large app for a major organisation. We wrote new parts of the app as a standalone Angular app, then converted it to an Angular Element and loaded that in the original legacy AngularJS app. To the user, there was no visual difference, but to use as development team, we could use this method to upgrade the entire app, bit by bit.
  4. Agree to use an industry standard to how to structure any new parts of your application – if you are going to upgrade your legacy Angular application to the latest version, either through the use of Angular Elements or through a gradual re-write. Then agreeing to use an industry-standard approach to how to structure the update application is an excellent idea. For example, you decide to use an approach like adopting NgRx as the way you are going to structure your Angular app, you’ll find that the developers on your team will enjoy working with a standard approach to developing the application. There would be more resources for them to make use of when looking for the best practice approach to solving a problem. They will enjoy developing an application they know that the new skillset they are learning can be used elsewhere in the industry and an employer it will be easier to get new developers on a project up to speed to be able to work on the project if it follows a well known standard approach.

Our app sounds like a legacy Angular app, what can we do?

If your team is struggling with a legacy Angular all is not lost. You can improve it without completely scrapping it and starting again. It just takes investment by both the development team and the end-user in believing that things may be hard to work with for a bit, but through using some or all of the ideas I’ve listed above. The application can be turned around from an old legacy application that is slow and hardly has any new features. To a much faster, useful application, where new features can be added in just a few weeks instead of months. Making both the developers of the project and end users happier.

If you feel that you need an Angular expert to help you with your legacy Angular app, then feel free to contact me.

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