autocomplete_item_search_live_2.html.eex

<script>
  function autocomplete() {
    return {
      // ...
      focus: 0,
      setFocus(f) {
        this.focus = f;
      },
      
      // ...
    }
  }
</script>

<!-- 
  Add the following two attributes to the <li> suggestion item
-->
<li 
  @mouseenter="setFocus(<%= index %>)"
  :class="{ 'focus': focus === <%= index %> }"
/>