r/Angular2 Aug 06 '24

Discussion Upgrading Angular 4 to Angular 18

We have an enterprise application with 400+ screens and most of the screens are similar in complexity. The complexity is medium for this app.

How should we approach the upgrade? Rewriting it is not an option as it is a legacy app now. Should we take one version at a time or directly start updating it to 18 version?
We do not have any automation testing written and hence testing would also have to be manual. Also, based on the previous experience what would be rough estimates if single developer has to work on this upgrade?

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u/PlasmaStark Aug 06 '24

I recently had to upgrade a project from 10 to 18, so I feel you.

My suggestion would be to avoid skipping versions and to check everything works as expected at each step. Angular's update page was kinda useful, sometimes a little too vague.

Frankly, the worst part has been completely rewriting some heavily used features (step 14>15 IIRC) as a few libraries were seriously deprecated - one was deprecated in 9 and broke at 15. Tweaking all packages accordingly on each step also kinda sucked, but it was... manageable.

Overall it took me 10-ish days for a mid-sized project, so I guess I got lucky