A service with inject() in Angular
Angular interview exercise on Dependency injection, difficulty 1 of 3. Solve it in the editor beside a worked example, or cold in Interview mode with the example hidden; the tests run the moment you do.
Write CartService, provided in root: an `items` signal of names, add(name) and a `count` computed. CartButtonComponent injects it, shows "Cart (N)" in a <span class="label"> and has a <button> that adds "Book".
Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Interview mode hides the example: solve it from memory, without the hint or the solution, and it counts as solved cold. Progress is saved in your browser, and in your account if you sign in.