subcategory.html

<!-- 1. First select binds its value to a new signal named 'category' -->
<!--    On change, it hits the /options endpoint, targeting the #subcategory -->
<select name="category"
        data-bind="category"
        data-on-change="@get('/options')">
  <option value="">Select a Category...</option>
  <option value="fruits">Fruits</option>
  <option value="vegetables">Vegetables</option>
</select>

<!-- 2. This container will receive the HTML from the backend. -->
<div id="subcategory">
  <!-- The backend will populate this -->
</div>