In the official documentation, you often see types denoted like this:
!Array.<string>= (e.g. here: https://docs.angularjs.org/api/ng/function/angular.module)
What does this mean? (especially the ! and = signs in my example)? Where is it explained? Is this a common standard somehow I was missing until now?
To cite the Angular guide on writing AngularJS Documentation
The AngularJS project uses a form of jsdoc for all of its documentation. (...) The flavour of jsdoc used by AngularJS is called ngdoc and is parsed by a Node.js utility called Dgeni.
here: http://usejsdoc.org/tags-type.html
So, e.g. the ! here means, that the parameter cannot be null.
The = means, that this parameter is optional.