I’m using TomSelect to create a multi-select dropdown in my project. I’ve added a “Select All” option and I’m trying to ensure that it always appears as the first item in the dropdown. However, despite my efforts, the “Select All” option does not consistently appear at the top of the list.

Here’s my current implementation:

function renderOptionItem(item, escape) {
  let img = item.src ? `<img class="me-2 tomselect-image" src="${escape(item.src)}" alt="icon" />` : '';
  let subtext = item.subtext ? `<div class="text-muted">${escape(item.subtext)}</div>` : '';
  return `<div class="d-flex align-items-center">
        ${img}
        <div>
        <div>${escape(item.text)}</div>
        ${subtext}
        </div>
      </div>`;
}

function updateSelectedItemsLabel(tomSelectInstance) {
  const selectedItems = tomSelectInstance.getValue();
  const selectedCount = selectedItems.length;
  const control = tomSelectInstance.control.querySelector('.items');

  if (selectedCount > 3 && control) {
    // Clear the control and add the summary item
    control.innerHTML = `<div class="item">Valgt ${selectedCount} elementer</div>`;
  } else {
    tomSelectInstance.refreshItems(); // Refresh to show actual selected items
  }

  // Update the "Select all" checkbox state
  const selectAllCheckbox = tomSelectInstance.dropdown_content.querySelector('.option[data-value="select-all"] input[type="checkbox"]');
  if (selectAllCheckbox) {
    const allItemValues = Object.keys(tomSelectInstance.options).filter(value => value !== 'select-all');
    selectAllCheckbox.checked = selectedItems.length === allItemValues.length;

    // Set a specific ID to the checkbox
    selectAllCheckbox.id = 'groupSelect-opt-0'; // Replace 'your-specific-id' with the desired ID
  }
}

function handleSelectAll(tomSelectInstance) {
  const allItems = tomSelectInstance.options;
  const allItemValues = Object.keys(allItems).filter(value => value !== 'select-all');
  const selectedItems = tomSelectInstance.getValue();

  if (selectedItems.length === allItemValues.length) {
    tomSelectInstance.clear(); // Deselect all if already selected
  } else {
    tomSelectInstance.setValue(allItemValues); // Select all
  }
}

function initializeTomSelect(selector, isSingleSelect = false) {
  const tomSelectInstance = new TomSelect(selector, {
    valueField: 'value',
    labelField: 'text',
    searchField: ['text', 'subtext'],
    render: {
      option: (item, escape) => {
        if (item.value === 'select-all') {
          return `<div class="d-flex align-items-center option">
                <div>Vælg alle</div>
              </div>`;
        } else {
          return renderOptionItem(item, escape);
        }
      },
      item: renderOptionItem
    },
    plugins: {
      'remove_button': {},
      'dropdown_input': {},
      'checkbox_options': {},
      'clear_button': {
        title: 'Ryd valgte' // Danish for "Clear selected"
      },
    },
    maxItems: isSingleSelect ? 1 : null,
    placeholder: isSingleSelect ? 'Vælg en mulighed...' : 'Vælg nogle muligheder...',
    create: false,
    allowEmptyOption: false, // Disallow empty options
    onInitialize: function() {
      if (isSingleSelect) {
        this.clear(); // Ensure no default selection
      }
      updateSelectedItemsLabel(this);

      // Add "Select all" option first
      this.addOption({ value: 'select-all', text: 'Vælg alle' });
      this.refreshOptions(false);

      // Ensure "Select all" is the first item
      const dropdownContent = this.dropdown_content;
      const selectAllOption = this.getOption('select-all');
      if (selectAllOption) {
        dropdownContent.insertBefore(selectAllOption, dropdownContent.firstChild);
      }

      dropdownContent.addEventListener('click', (event) => {
        const optionElement = event.target.closest('.option');
        if (optionElement && optionElement.getAttribute('data-value') === 'select-all') {
          event.stopPropagation(); // Prevent the dropdown from closing
          handleSelectAll(this);
          updateSelectedItemsLabel(this);
        }
      });
    },
    onItemAdd: function(value) {
      if (value !== 'select-all') {
        updateSelectedItemsLabel(this);
      }
    },
    onItemRemove: function() {
      updateSelectedItemsLabel(this);
    }
  });

  function moveSelectAllToTop(instance) {
    const dropdownContent = instance.dropdown_content;
    const selectAllOption = instance.getOption('select-all');
    if (selectAllOption) {
      dropdownContent.insertBefore(selectAllOption, dropdownContent.firstChild);
    }
  }

  // Handle the clear button functionality
  tomSelectInstance.on('clear', function() {
    tomSelectInstance.refreshItems();
  });

  // Handle changes to re-enable item removal if more than 3 selected
  tomSelectInstance.on('change', function() {
    const selectedItems = tomSelectInstance.getValue();
    const control = tomSelectInstance.control.querySelector('.items');

    if (selectedItems.length <= 3 && control && control.innerHTML.includes('elementer')) {
      tomSelectInstance.refreshItems(); // Refresh to show actual selected items
    }

    // Update the "Select all" checkbox state
    const selectAllCheckbox = tomSelectInstance.dropdown_content.querySelector('.option[data-value="select-all"] input[type="checkbox"]');
    if (selectAllCheckbox) {
      const allItemValues = Object.keys(tomSelectInstance.options).filter(value => value !== 'select-all');
      selectAllCheckbox.checked = selectedItems.length === allItemValues.length;
    }
  });
}

// Initialize Tom Select elements
document.addEventListener('DOMContentLoaded', function() {
  initializeTomSelect('#employeeSelect');
  initializeTomSelect('#entryTypeSelect', true); // Set isSingleSelect to true for entryTypeSelect
});

The Issue
Despite the code snippet above, the “Select All” option does not always appear as the first item in the dropdown. I’ve tried the following approaches:

1. Adding the “Select All” option first using this.addOption.
2. Manually moving the “Select All” option to the top using
   insertBefore.

However, these methods do not consistently result in the “Select All” option being at the top.

Expected Behavior
The “Select All” option should consistently appear as the first item in the dropdown list whenever the dropdown is opened.

Request for Help
I’m looking for guidance on how to ensure the “Select All” option always appears at the top of the dropdown list. Any insights or suggestions on how to achieve this would be greatly appreciated.