Custom validators in Angular
Angular interview exercise on Forms, difficulty 2 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.
Export forbiddenName(pattern): a validator giving { forbidden: { value } } when the control's value matches the RegExp. Export passwordsMatch: a group validator giving { mismatch: true } when `password` and `confirm` differ. SignupComponent uses both: username must not match /admin/i, and <small class="mismatch"> shows while the passwords differ.
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.