JavaScript — To-do list (class, private fields, async)

// A tiny in-memory to-do list: a class with private fields, arrow functions,
// template literals, array methods, a getter, and async/await.

class TodoList {
  #items = [];

  add(title, { priority = "normal" } = {}) {
    const item = { id: this.#items.length + 1, title, priority, done: false };
    this.#items.push(item);
    return item;
  }

  complete(id) {
    const item = this.#items.find((it) => it.id === id);
    if (!item) throw new Error(`No item with id ${id}`);
    item.done = true;
  }

  get pending() {
    return this.#items.filter((it) => !it.done);
  }

  toString() {
    return this.#items
      .map((it) => `${it.done ? "[x]" : "[ ]"} #${it.id} ${it.title} (${it.priority})`)
      .join("\n");
  }
}

async function main() {
  const list = new TodoList();
  list.add("Write tests", { priority: "high" });
  list.add("Ship release");
  list.complete(1);
  await Promise.resolve();
  console.log(list.toString());
  console.log(`${list.pending.length} item(s) left`);
}

main();