v-for with keys and v-if/v-else in Vue
Vue interview exercise on Templates & reactivity, 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.
Write TodoList with a prop `initial` (string[], default []): a <form> with an <input> and an Add <button> that appends the trimmed text as a todo (ignore blanks) and clears the input; <p class="empty">Nothing to do</p> while there are none, otherwise a <ul> with one <li> per todo (keyed by an id) that toggles the class "done" when clicked; and <p class="left">N left</p> counting the ones not done.
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.