basecoat/docs/_components/dropdown.njk

{% macro dropdown(
    id=None,
    trigger=None,
    main_attrs=None,
    trigger_attrs=None,
    menu_attrs=None
  )
%}
{% if registerComponent('dropdown') %}
<script>
  document.addEventListener('alpine:init', () => {
    Alpine.data('dropdown', () => ({
      open: false,
      focusedIndex: -1,
      menuItems: [],

      init() {
        this.$nextTick(() => {
          const menuElement = this.$el.querySelector('[role="menu"]');
          this.menuItems = Array.from(menuElement.querySelectorAll('[role=menuitem]'));
        });
      },
      
      $trigger: {
        '@click'() { this.handleClick() },
        '@keydown.down.prevent'() { this.open && this.nextItem() },
        ':aria-expanded'() { return this.open },
        ':aria-pressed'() { return this.open }
      },
      
      $menu: {
        '@click'(e) { this.handleMenuItemClick(e) },
        '@keydown.escape.window'() { this.handleEscape() },
        '@keydown.down.prevent'() { this.nextItem() },
        '@keydown.up.prevent'() { this.prevItem() },
        '@keydown.home.prevent'() { this.focusItem(0) },
        '@keydown.end.prevent'() { this.focusItem(this.menuItems.length - 1) },
        ':aria-hidden'() { return !this.open },
        'x-cloak': ''
      },
      
      focusItem(index) {
        if (index >= 0 && index < this.menuItems.length) {
          this.focusedIndex = index;
          this.menuItems[index].focus();
        }
      },
      
      nextItem() {
        this.focusItem((this.focusedIndex + 1) % this.menuItems.length);
      },
      
      prevItem() {
        this.focusItem(this.focusedIndex <= 0 ? this.menuItems.length - 1 : this.focusedIndex - 1);
      },
      
      handleClick() {
        this.open = !this.open;
        this.$nextTick(() => {
          if(this.open && this.menuItems.length) this.focusItem(0);
        });
      },
      
      handleEscape() {
        if (this.open) this.open = false;
      },
      
      handleMenuItemClick(event) {
        const menuItem = event.target.closest('[role=menuitem]');
        if (menuItem && !menuItem.disabled) {
          menuItem.blur();
          this.open = false;
        }
      },
    }));
  });
</script>
{% endif %}

<div
  class="dropdown {% if main_attrs %}{{ main_attrs.pop('class', '') }}{% endif %}"
  x-data="dropdown"
  @click.away="open = false"
  {% if id %}id="{{ id }}"{% endif %}
  {% for key, value in main_attrs %}
    {{ key }}="{{ value }}"
  {% endfor %}
>
  {% if trigger %}
  <button
    type="button"
    aria-haspopup="menu"
    aria-expanded="false"
    aria-pressed="false"
    x-bind="$trigger"
    {% if id %}
    id="{{ id }}-trigger"
    aria-controls="{{ id }}-menu"
    {% endif %}
    {% for key, value in trigger_attrs %}
      {{ key }}="{{ value }}"
    {% endfor %}
  >
    {{ trigger | safe }}
  </button>
  {% endif %}
  <nav
    role="menu"
    aria-orientation="vertical"
    aria-hidden="true"
    x-bind="$menu"
    {% if id %}id="{{ id }}-menu"{% endif %}
    {% for key, value in menu_attrs %}
      {{ key }}="{{ value }}"
    {% endfor %}
  >
    {{ caller() }}
  </nav>
</div>
{% endmacro %}