<nav id="site-navigation" class="main-navigation toggled">

      <button class="menu-toggle" aria-controls="primary-menu" aria-expanded="true">
              <a href="#"> Кнопка</a>     
      </button>



      <div class="center"> 
            <ul id="primary-menu" class="menu nav-menu">
              <li class="menu-item menu-item-type-custom menu-item-object-custom menu-item-has-children menu-item-914"><a href="#">На клик реагирует / тап не реагирует</a>
                <ul class="sub-menu">
                  <li class="menu-item menu-item-type-post_type menu-item-object-page menu-item-915"><a href="#">sub menu 1</a></li>
                  <li class="menu-item menu-item-type-post_type menu-item-object-page menu-item-109"><a href="#">sub menu 2</a></li>
                </ul>
             </li>
            </ul>
      </div>
    </nav>




.center {
    overflow: hidden;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    height: 80vh;
}


ul li a {
    display: flex;
    align-items: center;
    justify-content: center;
    flex-direction: column;
}



ul.sub-menu {
    display: none;
}

ul.sub-menu.display-block {
    display: block;
}
/**
 * File navigation.js.
 *
 * Handles toggling the navigation menu for small screens and enables TAB key
 * navigation support for dropdown menus.
 */
( function() {
  const siteNavigation = document.getElementById( 'site-navigation' );

  // Return early if the navigation don't exist.
  if ( ! siteNavigation ) {
    return;
  }

  const button = siteNavigation.getElementsByTagName( 'button' )[ 0 ];

  // Return early if the button don't exist.
  if ( 'undefined' === typeof button ) {
    return;
  }

  const menu = siteNavigation.getElementsByTagName( 'ul' )[ 0 ];

  // Hide menu toggle button if menu is empty and return early.
  if ( 'undefined' === typeof menu ) {
    button.style.display = 'none';
    return;
  }

  if ( ! menu.classList.contains( 'nav-menu' ) ) {
    menu.classList.add( 'nav-menu' );
  }

  // Toggle the .toggled class and the aria-expanded value each time the button is clicked.
  button.addEventListener( 'click', function() {
    siteNavigation.classList.toggle( 'toggled' );

    if ( button.getAttribute( 'aria-expanded' ) === 'true' ) {
      button.setAttribute( 'aria-expanded', 'false' );
    } else {
      button.setAttribute( 'aria-expanded', 'true' );
    }
  } );

  // Remove the .toggled class and set aria-expanded to false when the user clicks outside the navigation.
  document.addEventListener( 'click', function( event ) {
    const isClickInside = siteNavigation.contains( event.target );

    if ( ! isClickInside ) {
      siteNavigation.classList.remove( 'toggled' );
      button.setAttribute( 'aria-expanded', 'false' );
    }
  } );

  // Get all the link elements within the menu.
  const links = menu.getElementsByTagName( 'a' );

  // Get all the link elements with children within the menu.
  const linksWithChildren = menu.querySelectorAll( '.menu-item-has-children > a, .page_item_has_children > a' );

  // Toggle focus each time a menu link is focused or blurred.
  for ( const link of links ) {
    link.addEventListener( 'focus', toggleFocus, true );
    link.addEventListener( 'blur', toggleFocus, true );
  }

  // Toggle focus each time a menu link with children receive a touch event.
  for ( const link of linksWithChildren ) {
    link.addEventListener( 'touchstart', toggleFocus, false );
  }

  /**
   * Sets or removes .focus class on an element.
   */
  function toggleFocus() {
    if ( event.type === 'focus' || event.type === 'blur' ) {
      let self = this;
      // Move up through the ancestors of the current link until we hit .nav-menu.
      while ( ! self.classList.contains( 'nav-menu' ) ) {
        // On li elements toggle the class .focus.
        if ( 'li' === self.tagName.toLowerCase() ) {
          self.classList.toggle( 'focus' );
        }
        self = self.parentNode;
      }
    }

    if ( event.type === 'touchstart' ) {
      const menuItem = this.parentNode;
      event.preventDefault();
      for ( const link of menuItem.parentNode.children ) {
        if ( menuItem !== link ) {
          link.classList.remove( 'focus' );
        }
      }
      menuItem.classList.toggle( 'focus' );
    }
  }
}() );












document.querySelector('li.menu-item-has-children a').onclick = function() {
    document.querySelector('ul.sub-menu').classList.toggle('display-block');
    document.querySelector('li.menu-item-has-children a').classList.toggle('arrow-up');
}

External CSS

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External JavaScript

This Pen doesn't use any external JavaScript resources.