Pen Settings

HTML

CSS

CSS Base

Vendor Prefixing

Add External Stylesheets/Pens

Any URL's added here will be added as <link>s in order, and before the CSS in the editor. If you link to another Pen, it will include the CSS from that Pen. If the preprocessor matches, it will attempt to combine them before processing.

+ add another resource

JavaScript

Babel is required to process package imports. If you need a different preprocessor remove all packages first.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

+ add another resource

Behavior

Save Automatically?

If active, Pens will autosave every 30 seconds after being saved once.

Auto-Updating Preview

If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.

Format on Save

If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.

Editor Settings

Code Indentation

Want to change your Syntax Highlighting theme, Fonts and more?

Visit your global Editor Settings.

HTML

              
                <label for="select-el" class="combo-label">Native select element</label>
<div class="combo">
  <select id="select-el" class="combo-input">
    <option>Apple</option>
    <option>Banana</option>
    <option>Cherry</option>
    <option>Durian</option>
    <option>Eggplant</option>
    <option>Fig</option>
    <option>Guava</option>
    <option>Huckleberry</option>
  </select>
</div>

<label for="combo1" class="combo-label">ARIA 1.1 combobox with readonly input</label>
<div class="combo js-aria11">
  <div role="combobox" aria-haspopup="listbox" aria-expanded="false" aria-owns="listbox1" class="input-wrapper">
    <input
           aria-activedescendant=""
           aria-autocomplete="none"
           id="combo1"
           class="combo-input"
           readonly
           type="text">
    <div class="combo-menu" role="listbox" id="listbox1"></div>
  </div>
</div>

<label id="combo2-label" class="combo-label">Read-only combobox with no input</label>
<div class="combo js-select">
  <div
       aria-activedescendant=""
       aria-autocomplete="none"
       aria-owns="listbox2"
       aria-expanded="false"
       aria-haspopup="listbox"
       aria-labelledby="combo2-label"
       id="combo2"
       class="combo-input"
       role="combobox"
       tabindex="0"
       ></div>
  <div class="combo-menu" role="listbox" id="listbox2"></div>
</div>

<label id="popup-label" class="combo-label">Popup Button + listbox</label>
<div class="combo js-popup-button">
  <button
          aria-expanded="false"
          aria-haspopup="listbox"
          aria-labelledby="popup-label popup"
          class="combo-input"
          id="popup"
          type="button"
          ></button>
  <div aria-activedescendant="" class="combo-menu" role="listbox" tabindex="-1"></div>
</div>

<label id="listbox-label" class="combo-label">Listbox with aria-expanded</label>
<div class="combo js-listbox">
  <div
       aria-activedescendant=""
       aria-expanded="false"
       aria-labelledby="listbox-label listbox-current"
       id="dropdown-listbox"
       class="input-wrapper"
       role="listbox"
       tabindex="0"
       >
    <div class="combo-input" role="presentation" id="listbox-current"></div>
    <div class="combo-menu" role="presentation"></div>
  </div>
</div>
              
            
!

CSS

              
                *, *::before, *::after {
  box-sizing: border-box;
}

body {
  background-color: #f5f5f5;
  font-family: "Segoe UI", SegoeUI, "Helvetica Neue", Helvetica, Arial, sans-serif;
  font-size: 120%;
  line-height: 1.4;
  margin: 0;
  padding: 2em;
}

.combo {
  display: block;
  margin-bottom: 1.5em;
  max-width: 400px;
  position: relative;
}

.combo::after {
  border-bottom: 2px solid rgba(0,0,0,.5);
  border-right: 2px solid rgba(0,0,0,.5);
  content: '';
  display: block;
  height: 12px;
  pointer-events: none;
  position: absolute;
  right: 16px;
  top: 50%;
  transform: translate(0, -65%) rotate(45deg);
  width: 12px;
}

.input-wrapper {
  border-radius: 4px;
}

.combo-input {
  background-color: #f5f5f5;
  border: 2px solid rgba(0,0,0,.5);
  border-radius: 4px;
  display: block;
  font-size: 1em;
  min-height: calc(1.4em + 26px);
  padding: 12px 16px 14px;
  text-align: left;
  width: 100%;
}

select.combo-input {
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
}

.open .combo-input {
  border-radius: 4px 4px 0 0;
}

.combo-input:focus,
.combo-menu:focus,
.input-wrapper:focus {
  border-color: #0067b8;
  box-shadow: 0 0 4px 2px #0067b8;
  outline: 5px solid transparent;
}

.combo-label {
  display: block;
  font-size: 20px;
  font-weight: 100;
  margin-bottom: 0.25em;
}

.combo-menu {
  background-color: #f5f5f5;
  border: 1px solid rgba(0,0,0,.42);
  border-radius: 0 0 4px 4px;
  display: none;
  max-height: 300px;
  overflow-y:scroll;
  left: 0;
  position: absolute;
  top: 100%;
  width: 100%;
  z-index: 100;
}

.open .combo-menu {
  display: block;
}

.combo-option {
  padding: 10px 12px 12px;
}

.combo-option.option-current,
.combo-option:hover {
  background-color: rgba(0,0,0,0.1);
}

.combo-option.option-selected {
  padding-right: 30px;
  position: relative;
}

.combo-option.option-selected::after {
  border-bottom: 2px solid #000;
  border-right: 2px solid #000;
  content: '';
  height: 16px;
  position: absolute;
  right: 15px;
  top: 50%;
  transform: translate(0, -50%) rotate(45deg);
  width: 8px;
}

/* multiselect list of selected options */
.selected-options {
  list-style-type: none;
  margin: 0;
  max-width: 400px;
  padding: 0;
}

.selected-options li {
  display: inline-block;
  margin-bottom: 5px;
}
              
            
!

JS

              
                /*
 * Helper constants and functions
 */

// make it easier for ourselves by putting some values in objects
// in TypeScript, these would be enums
const Keys = {
  Backspace: 'Backspace',
  Clear: 'Clear',
  Down: 'ArrowDown',
  End: 'End',
  Enter: 'Enter',
  Escape: 'Escape',
  Home: 'Home',
  Left: 'ArrowLeft',
  PageDown: 'PageDown',
  PageUp: 'PageUp',
  Right: 'ArrowRight',
  Space: ' ',
  Tab: 'Tab',
  Up: 'ArrowUp'
}

const MenuActions = {
  Close: 0,
  CloseSelect: 1,
  First: 2,
  Last: 3,
  Next: 4,
  Open: 5,
  Previous: 6,
  Select: 7,
  Space: 8,
  Type: 9
}

// filter an array of options against an input string
// returns an array of options that begin with the filter string, case-independent
function filterOptions(options = [], filter, exclude = []) {
  return options.filter((option) => {
    const matches = option.toLowerCase().indexOf(filter.toLowerCase()) === 0;
    return matches && exclude.indexOf(option) < 0;
  });
}

// return an array of exact option name matches from a comma-separated string
function findMatches(options, search) {
  const names = search.split(',');
  return names.map((name) => {
    const match = options.filter((option) => name.trim().toLowerCase() === option.toLowerCase());
    return match.length > 0 ? match[0] : null;
  })
  .filter((option) => option !== null);
}

// return combobox action from key press
function getActionFromKey(key, menuOpen) {
  // handle opening when closed
  if (!menuOpen && key === Keys.Down) {
    return MenuActions.Open;
  }

  // handle keys when open
  if (key === Keys.Down) {
    return MenuActions.Next;
  }
  else if (key === Keys.Up) {
    return MenuActions.Previous;
  }
  else if (key === Keys.Home) {
    return MenuActions.First;
  }
  else if (key === Keys.End) {
    return MenuActions.Last;
  }
  else if (key === Keys.Escape) {
    return MenuActions.Close;
  }
  else if (key === Keys.Enter) {
    return MenuActions.CloseSelect;
  }
  else if (key === Keys.Backspace || key === Keys.Clear || key.length === 1) {
    return MenuActions.Type;
  }
}

// get index of option that matches a string
function getIndexByLetter(options, filter) {
  const firstMatch = filterOptions(options, filter)[0];
  return firstMatch ? options.indexOf(firstMatch) : -1;
}

// get updated option index
function getUpdatedIndex(current, max, action) {
  switch(action) {
    case MenuActions.First:
      return 0;
    case MenuActions.Last:
      return max;
    case MenuActions.Previous:
      return Math.max(0, current - 1);
    case MenuActions.Next:
      return Math.min(max, current + 1);
    default:
      return current;
  }
}

// check if an element is currently scrollable
function isScrollable(element) {
  return element && element.clientHeight < element.scrollHeight;
}

// ensure given child element is within the parent's visible scroll area
function maintainScrollVisibility(activeElement, scrollParent) {
  const { offsetHeight, offsetTop } = activeElement;
  const { offsetHeight: parentOffsetHeight, scrollTop } = scrollParent;

  const isAbove = offsetTop < scrollTop;
  const isBelow = (offsetTop + offsetHeight) > (scrollTop + parentOffsetHeight);

  if (isAbove) {
    scrollParent.scrollTo(0, offsetTop);
  }
  else if (isBelow) {
    scrollParent.scrollTo(0, offsetTop - parentOffsetHeight + offsetHeight);
  }
}

/*
 * ARIA 1.1 Readonly Input code
 */
const ARIA11Combo = function(el, options) {
  // element refs
  this.el = el;
  this.comboEl = el.querySelector('[role=combobox]')
  this.inputEl = el.querySelector('input');
  this.listboxEl = el.querySelector('[role=listbox]');

  // data
  this.idBase = this.inputEl.id;
  this.options = options;

  // state
  this.activeIndex = 0;
  this.open = false;
}

ARIA11Combo.prototype.init = function() {
  this.inputEl.addEventListener('input', this.onInput.bind(this));
  this.inputEl.addEventListener('blur', this.onInputBlur.bind(this));
  this.inputEl.addEventListener('click', () => this.updateMenuState(true));
  this.inputEl.addEventListener('keydown', this.onInputKeyDown.bind(this));

  this.options.map((option, index) => {
    const optionEl = document.createElement('div');
    optionEl.setAttribute('role', 'option');
    optionEl.id = `${this.idBase}-${index}`;
    optionEl.className = index === 0 ? 'combo-option option-current' : 'combo-option';
    optionEl.setAttribute('aria-selected', 'false');
    optionEl.innerText = option;

    optionEl.addEventListener('click', () => { this.onOptionClick(index); });
    optionEl.addEventListener('mousedown', this.onOptionMouseDown.bind(this));

    this.listboxEl.appendChild(optionEl);
  });
}

ARIA11Combo.prototype.onInput = function() {
  const curValue = this.inputEl.value;
  const matches = filterOptions(this.options, curValue);

  // set activeIndex to first matching option
  // (or leave it alone, if the active option is already in the matching set)
  const filterCurrentOption = matches.filter((option) => option === this.options[this.activeIndex]);
  if (matches.length > 0 && !filterCurrentOption.length) {
    this.onOptionChange(this.options.indexOf(matches[0]));
  }

  const menuState = this.options.length > 0;
  if (this.open !== menuState) {
    this.updateMenuState(menuState, false);
  }
}

ARIA11Combo.prototype.onInputKeyDown = function(event) {
  const { key } = event;
  const max = this.options.length - 1;

  const action = getActionFromKey(key, this.open);

  switch(action) {
    case MenuActions.Next:
    case MenuActions.Last:
    case MenuActions.First:
    case MenuActions.Previous:
      event.preventDefault();
      return this.onOptionChange(getUpdatedIndex(this.activeIndex, max, action));
    case MenuActions.CloseSelect:
      event.preventDefault();
      this.selectOption(this.activeIndex);
      return this.updateMenuState(false);
    case MenuActions.Close:
      event.preventDefault();
      return this.updateMenuState(false);
    case MenuActions.Type:
      this.onOptionChange(Math.max(0, getIndexByLetter(this.options, key)));
    case MenuActions.Open:
      return this.updateMenuState(true);
  }
}

ARIA11Combo.prototype.onInputBlur = function() {
  if (this.ignoreBlur) {
    this.ignoreBlur = false;
    return;
  }

  if (this.open) {
    this.updateMenuState(false, false);
  }
}

ARIA11Combo.prototype.onOptionChange = function(index) {
  this.activeIndex = index;
  this.inputEl.setAttribute('aria-activedescendant', `${this.idBase}-${index}`);

  // update active style
  const options = this.el.querySelectorAll('[role=option]');
  [...options].forEach((optionEl) => {
    optionEl.classList.remove('option-current');
  });
  options[index].classList.add('option-current');

  if (this.open && isScrollable(this.listboxEl)) {
    maintainScrollVisibility(options[index], this.listboxEl);
  }
}

ARIA11Combo.prototype.onOptionClick = function(index) {
  this.onOptionChange(index);
  this.selectOption(index);
  this.updateMenuState(false);
}

ARIA11Combo.prototype.onOptionMouseDown = function() {
  this.ignoreBlur = true;
}

ARIA11Combo.prototype.selectOption = function(index) {
  const selected = this.options[index];
  this.inputEl.value = selected;
  this.activeIndex = index;

  // update aria-selected
  const options = this.el.querySelectorAll('[role=option]');
  [...options].forEach((optionEl) => {
    optionEl.setAttribute('aria-selected', 'false');
  });
  options[index].setAttribute('aria-selected', 'true');
}

ARIA11Combo.prototype.updateMenuState = function(open, callFocus = true) {
  this.open = open;

  this.comboEl.setAttribute('aria-expanded', `${open}`);
  open ? this.el.classList.add('open') : this.el.classList.remove('open');
  callFocus && this.inputEl.focus();
}

// init combo
const aria11El = document.querySelector('.js-aria11');
const options = ['Apple', 'Banana', 'Cherry', 'Durian', 'Eggplant', 'Fig', 'Guava', 'Huckleberry'];
const aria11Component = new ARIA11Combo(aria11El, options);
aria11Component.init();

/*
 * Read-only combobox with no input code
 */
 const NoInput = function(el, options) {
  // element refs
  this.el = el;
  this.comboEl = el.querySelector('[role=combobox]');
  this.listboxEl = el.querySelector('[role=listbox]');

  // data
  this.idBase = this.comboEl.id;
  this.options = options;

  // state
  this.activeIndex = 0;
  this.open = false;
}

NoInput.prototype.init = function() {
  this.comboEl.addEventListener('blur', this.onComboBlur.bind(this));
  this.comboEl.addEventListener('click', () => this.updateMenuState(true));
  this.comboEl.addEventListener('keydown', this.onComboKeyDown.bind(this));

  this.options.map((option, index) => {
    const optionEl = document.createElement('div');
    optionEl.setAttribute('role', 'option');
    optionEl.id = `${this.idBase}-${index}`;
    optionEl.className = index === 0 ? 'combo-option option-current' : 'combo-option';
    optionEl.setAttribute('aria-selected', 'false');
    optionEl.innerText = option;

    optionEl.addEventListener('click', (event) => {
      event.stopPropagation();
      this.onOptionClick(index);
    });
    optionEl.addEventListener('mousedown', this.onOptionMouseDown.bind(this));

    this.listboxEl.appendChild(optionEl);
  });
}

NoInput.prototype.onComboKeyDown = function(event) {
  const { key } = event;
  const max = this.options.length - 1;

  const action = getActionFromKey(key, this.open);

  switch(action) {
      case MenuActions.Next:
      case MenuActions.Last:
      case MenuActions.First:
      case MenuActions.Previous:
        event.preventDefault();
        return this.onOptionChange(getUpdatedIndex(this.activeIndex, max, action));
      case MenuActions.CloseSelect:
      case MenuActions.Space:
        event.preventDefault();
        this.selectOption(this.activeIndex);
      case MenuActions.Close:
        event.preventDefault();
        return this.updateMenuState(false);
      case MenuActions.Type:
        this.updateMenuState(true);
        return this.onOptionChange(Math.max(0, getIndexByLetter(this.options, key)));
      case MenuActions.Open:
        event.preventDefault();
        return this.updateMenuState(true);
    }
}

NoInput.prototype.onComboBlur = function() {
  if (this.ignoreBlur) {
    this.ignoreBlur = false;
    return;
  }

  if (this.open) {
    this.updateMenuState(false, false);
  }
}

NoInput.prototype.onOptionChange = function(index) {
  this.activeIndex = index;
  this.comboEl.setAttribute('aria-activedescendant', `${this.idBase}-${index}`);

  // update active style
  const options = this.el.querySelectorAll('[role=option]');
  [...options].forEach((optionEl) => {
    optionEl.classList.remove('option-current');
  });
  options[index].classList.add('option-current');

  if (isScrollable(this.listboxEl)) {
    maintainScrollVisibility(options[index], this.listboxEl);
  }
}

NoInput.prototype.onOptionClick = function(index) {
  this.onOptionChange(index);
  this.selectOption(index);
  this.updateMenuState(false);
}

NoInput.prototype.onOptionMouseDown = function() {
  this.ignoreBlur = true;
}

NoInput.prototype.selectOption = function(index) {
  const selected = this.options[index];
  this.comboEl.innerHTML = selected;
  this.activeIndex = index;

  // update aria-selected
  const options = this.el.querySelectorAll('[role=option]');
  [...options].forEach((optionEl) => {
    optionEl.setAttribute('aria-selected', 'false');
  });
  options[index].setAttribute('aria-selected', 'true');
}

NoInput.prototype.updateMenuState = function(open, callFocus = true) {
  this.open = open;

  this.comboEl.setAttribute('aria-expanded', `${open}`);
  open ? this.el.classList.add('open') : this.el.classList.remove('open');
  callFocus && this.comboEl.focus();
}

// init select
const selectEl = document.querySelector('.js-select');
const selectComponent = new NoInput(selectEl, options);
selectComponent.init();

/*
 * Popup button (mac pattern) code
 */
 const PopupButton = function(el, options) {
  // element refs
  this.el = el;
  this.buttonEl = el.querySelector('button');
  this.listboxEl = el.querySelector('[role=listbox]');

  // data
  this.idBase = this.buttonEl.id;
  this.options = options;

  // state
  this.activeIndex = 0;
  this.open = false;
}

PopupButton.prototype.init = function() {
  this.buttonEl.addEventListener('blur', this.onComboBlur.bind(this));
  this.buttonEl.addEventListener('click', () => this.updateMenuState(true));
  this.buttonEl.addEventListener('keydown', this.onButtonKeyDown.bind(this));

  this.listboxEl.addEventListener('blur', this.onComboBlur.bind(this));
  this.listboxEl.addEventListener('keydown', this.onListboxKeyDown.bind(this));

  this.options.map((option, index) => {
    const optionEl = document.createElement('div');
    optionEl.setAttribute('role', 'option');
    optionEl.id = `${this.idBase}-${index}`;
    optionEl.className = index === 0 ? 'combo-option option-current' : 'combo-option';
    optionEl.setAttribute('aria-selected', 'false');
    optionEl.innerText = option;

    optionEl.addEventListener('click', () => { this.onOptionClick(index); });
    optionEl.addEventListener('mousedown', this.onOptionMouseDown.bind(this));

    this.listboxEl.appendChild(optionEl);
  });
}

PopupButton.prototype.onButtonKeyDown = function(event) {
  const { key } = event;
  const action = getActionFromKey(key, this.open);

  switch(action) {
    case MenuActions.Close:
      event.preventDefault();
      return this.updateMenuState(false);
    case MenuActions.Type:
      this.onOptionChange(Math.max(0, getIndexByLetter(this.options, key)));
    case MenuActions.Open:
      return this.updateMenuState(true);
  }
}

PopupButton.prototype.onComboBlur = function() {
  if (this.ignoreBlur) {
    this.ignoreBlur = false;
    return;
  }

  this.updateMenuState(false, false);
}

PopupButton.prototype.onListboxKeyDown = function(event) {
  const { key } = event;
  const max = this.options.length - 1;
  const action = getActionFromKey(key, this.open);

  switch(action) {
    case MenuActions.Next:
    case MenuActions.Last:
    case MenuActions.First:
    case MenuActions.Previous:
      event.preventDefault();
      return this.onOptionChange(getUpdatedIndex(this.activeIndex, max, action));
    case MenuActions.CloseSelect:
      this.selectOption(this.activeIndex);
    case MenuActions.Close:
      event.preventDefault();
      return this.updateMenuState(false);
    case MenuActions.Type:
      this.onOptionChange(Math.max(0, getIndexByLetter(this.options, key)));
      break;
  }
}

PopupButton.prototype.onOptionChange = function(index) {
  this.activeIndex = index;
  this.listboxEl.setAttribute('aria-activedescendant', `${this.idBase}-${index}`);

  // update active style
  const options = this.el.querySelectorAll('[role=option]');
  [...options].forEach((optionEl) => {
    optionEl.classList.remove('option-current');
  });
  options[index].classList.add('option-current');

  if (this.open && isScrollable(this.listboxEl)) {
    maintainScrollVisibility(options[index], this.listboxEl);
  }
}

PopupButton.prototype.onOptionClick = function(index) {
  this.onOptionChange(index);
  this.selectOption(index);
  this.updateMenuState(false);
}

PopupButton.prototype.onOptionMouseDown = function() {
  this.ignoreBlur = true;
}

PopupButton.prototype.selectOption = function(index) {
  const selected = this.options[index];
  this.buttonEl.innerHTML = selected;
  this.activeIndex = index;

  // update aria-selected
  const options = this.el.querySelectorAll('[role=option]');
  [...options].forEach((optionEl) => {
    optionEl.setAttribute('aria-selected', 'false');
  });
  options[index].setAttribute('aria-selected', 'true');
}

PopupButton.prototype.updateMenuState = function(open, callFocus = true) {
  this.open = open;

  this.buttonEl.setAttribute('aria-expanded', `${open}`);
  open ? this.el.classList.add('open') : this.el.classList.remove('open');

  const focusEl = open ? this.listboxEl : this.buttonEl;
  this.ignoreBlur = callFocus;
  callFocus && focusEl.focus();
}

// init combo
const popupEl = document.querySelector('.js-popup-button');
const popupButtonComponent = new PopupButton(popupEl, options);
popupButtonComponent.init();

/*
 * Expanding Listbox code
 */
 const ListboxDropdown = function(el, options) {
  // element refs
  this.el = el;
  this.listboxEl = el.querySelector('[role=listbox]');
  this.valueEl = el.querySelector('.combo-input');
  this.optionsEl = el.querySelector('.combo-menu');

  // data
  this.idBase = this.listboxEl.id;
  this.options = options;

  // state
  this.activeIndex = 0;
  this.open = false;
}

ListboxDropdown.prototype.init = function() {
  this.listboxEl.addEventListener('blur', this.onListboxBlur.bind(this));
  this.listboxEl.addEventListener('keydown', this.onListboxKeyDown.bind(this));

  this.valueEl.addEventListener('click', () => this.updateMenuState(true));


  this.options.map((option, index) => {
    const optionEl = document.createElement('div');
    optionEl.setAttribute('role', 'option');
    optionEl.id = `${this.idBase}-${index}`;
    optionEl.className = index === 0 ? 'combo-option option-current' : 'combo-option';
    optionEl.setAttribute('aria-selected', 'false');
    optionEl.innerText = option;

    optionEl.addEventListener('click', () => { this.onOptionClick(index); });
    optionEl.addEventListener('mousedown', this.onOptionMouseDown.bind(this));

    this.optionsEl.appendChild(optionEl);
  });
}

ListboxDropdown.prototype.onListboxBlur = function() {
  if (this.ignoreBlur) {
    this.ignoreBlur = false;
    return;
  }

  this.updateMenuState(false);
}

ListboxDropdown.prototype.onListboxKeyDown = function(event) {
  const { key } = event;
  const max = this.options.length - 1;
  const action = getActionFromKey(key, this.open);

  switch(action) {
    case MenuActions.Open:
      return this.updateMenuState(true);
    case MenuActions.Next:
    case MenuActions.Last:
    case MenuActions.First:
    case MenuActions.Previous:
      event.preventDefault();
      return this.onOptionChange(getUpdatedIndex(this.activeIndex, max, action));
    case MenuActions.CloseSelect:
      this.selectOption(this.activeIndex);
    case MenuActions.Close:
      event.preventDefault();
      return this.updateMenuState(false);
    case MenuActions.Type:
      this.onOptionChange(Math.max(0, getIndexByLetter(this.options, key)));
      break;
  }
}

ListboxDropdown.prototype.onOptionChange = function(index) {
  this.activeIndex = index;
  this.listboxEl.setAttribute('aria-activedescendant', `${this.idBase}-${index}`);

  // update active style
  const options = this.el.querySelectorAll('[role=option]');
  [...options].forEach((optionEl) => {
    optionEl.classList.remove('option-current');
  });
  options[index].classList.add('option-current');

  if (this.open && isScrollable(this.optionsEl)) {
    maintainScrollVisibility(options[index], this.optionsEl);
  }
}

ListboxDropdown.prototype.onOptionClick = function(index) {
  this.onOptionChange(index);
  this.selectOption(index);
  this.updateMenuState(false);
}

ListboxDropdown.prototype.onOptionMouseDown = function() {
  this.ignoreBlur = true;
}

ListboxDropdown.prototype.selectOption = function(index) {
  const selected = this.options[index];
  this.valueEl.innerHTML = selected;
  this.activeIndex = index;

  // update aria-selected
  const options = this.el.querySelectorAll('[role=option]');
  [...options].forEach((optionEl) => {
    optionEl.setAttribute('aria-selected', 'false');
  });
  options[index].setAttribute('aria-selected', 'true');
}

ListboxDropdown.prototype.updateMenuState = function(open) {
  this.open = open;

  this.listboxEl.setAttribute('aria-expanded', `${open}`);
  open ? this.el.classList.add('open') : this.el.classList.remove('open');
}

// init combo
const listboxEl = document.querySelector('.js-listbox');
const listboxComponent = new ListboxDropdown(listboxEl, options);
listboxComponent.init();
              
            
!
999px

Console