Upgrading Components Strategically

Services that have no dependencies are excellent candidates for conversion. Once converted to Angular 2, services can be downgraded to work in Angular 1.x. Components can follow a similar strategy, with "leaf" components being converted before "root" components.

Possibly the most challenging component/service to upgrade is Angular 1.x's UI Router library. This process might be simplified in the future, but for the moment it's best to upgrade UI Router last.