Angular 2 documentation is managed as code,
with unit tests that are included main software release acceptance tests.
This way documentation is always in sync with framework.
Angular Docs - index
angular.js/docs at master · angular/angular.js · GitHub
Angular 2 Docs with Ward Bell @ .NET Rocks! vNext
"Ward Bell is serving as editor in chief for Angular docs. After complaining about the quality problems with the Angular documentation, Ward found himself in charge of the problem - and has taken it on in a big way. The docs themselves are developed in GitHub, so anyone can contribute. The challenge is making sure they're good - everything is driven by coding samples that are as simple as they need to be and follow strict standards. The result is docs you can trust - first and foremost they are correct, and hopefully effective at getting you productive with Angular"