angular-migration

Migrate AngularJS to Angular incrementally using ngUpgrade, which runs both frameworks side-by-side in a hybrid app. Migrate services first, then convert controllers and directives to components feature by feature, testing continuously before removing AngularJS code.

The incremental hybrid approach suits large apps needing continuous delivery, big-bang rewrites fit small apps, and vertical slices work for medium apps with distinct features. Choose based on codebase size, team capacity, and release cadence.

Use downgradeInjectable from @angular/upgrade/static to register an Angular service as an AngularJS factory. Then inject it into AngularJS controllers by the registered name, allowing shared logic during hybrid migration.

Yes, during hybrid migration both routers can coexist, but ownership of routes must be clearly divided between $routeProvider and Angular Router. Migrate routes incrementally, moving each path to Angular Router as its feature is converted.

Avoid incremental migration for small apps where a complete rewrite is faster, or when the app is already on a modern Angular version. It is also unnecessary for minor UI fixes that require no framework changes.