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HTML

              
                <div class="accordion">
  <h2>
    <button id="accordion-trigger-1" aria-expanded="false" class="accordion__trigger" aria-controls="accordion-content-1">Accordion Title 1</button>

  </h2>
  <div class="accordion__content" id="accordion-content-1" aria-labelledby="accordion-trigger-1">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec at bibendum nunc. Etiam justo leo, suscipit non ex id, rhoncus viverra neque. Maecenas convallis ex vel arcu porta, ornare faucibus dolor iaculis. Ut rutrum felis eget rutrum commodo. Lorem
    ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  <h2>
    <button id="accordion-trigger-2" aria-expanded="false" class="accordion__trigger" aria-controls="accordion-content-2">Accordion Title 2</button>

  </h2>
  <div class="accordion__content" id="accordion-content-2" aria-labelledby="accordion-trigger-2">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec at bibendum nunc. Etiam justo leo, suscipit non ex id, rhoncus viverra neque. Maecenas convallis ex vel arcu porta, ornare faucibus dolor iaculis. Ut rutrum felis eget rutrum commodo. Lorem
    ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
<h2>
    <button id="accordion-trigger-3" aria-expanded="false" class="accordion__trigger" aria-controls="accordion-content-3">Accordion Title 3</button>

  </h2>
  <div class="accordion__content" id="accordion-content-3" aria-labelledby="accordion-trigger-3">
    Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec at bibendum nunc. Etiam justo leo, suscipit non ex id, rhoncus viverra neque. Maecenas convallis ex vel arcu porta, ornare faucibus dolor iaculis. Ut rutrum felis eget rutrum commodo. Lorem
    ipsum dolor sit amet, consectetur adipiscing elit.
  </div>
  
</div>
              
            
!

CSS

              
                body {
  font-family: Helvetica, Arial, Verdana;
}

.accordion {
  
   width: 400px;
  
  &__trigger {
    padding: 10px;
    padding-top: 20px;
    padding-bottom: 20px;
    background-color: #ccc;
    border-width: 0px;
    color: #000;
    font-size:1rem;
    display: block;
    width:100%;
    text-align: left;    
    border-bottom: 1px solid #666;
  }
  
  &__content {
    padding: 10px;
    line-height:1.2;
    display: none;
    
    &--expanded {
      display: block;
    }
  }
  
}
              
            
!

JS

              
                const triggers = document.querySelectorAll('.accordion__trigger');

triggers.forEach(
  function(item, index) {
    
    //
    // Add click handler
    //
    item.addEventListener(
      'click', 
      function() {
        return accordion_toggle(item);
      }
    );
    
    //
    // Add keyboard handlers
    // Borrowed from https://www.w3.org/TR/wai-aria-practices/examples/accordion/accordion.html
    //
    item.addEventListener(
      'keydown', 
      function(event) {
        
        let trigger_arr = Array.prototype.slice.call( triggers );
        let target = event.target;
        let key = event.which.toString();
        let ctrl_modifier = (event.ctrlKey && key.match(/33|34/));

        if (key.match(/38|40/) || ctrl_modifier) {
          let index = trigger_arr.indexOf(target);
          let direction = (key.match(/34|40/)) ? 1 : -1;
          let length = triggers.length;
          let newIndex = (index + length + direction) % length;

          trigger_arr[newIndex].focus();

          event.preventDefault();
        }
        else if (key.match(/35|36/)) {
          // 35 = End, 36 = Home keyboard operations
          switch (key) {
            // Go to first accordion
            case '36':
              trigger_arr[0].focus();
              break;
              // Go to last accordion
            case '35':
              trigger_arr[trigger_arr.length - 1].focus();
              break;
          }
          event.preventDefault();
        }
      }
    );
    
  }
);

function accordion_toggle(trigger_item) {
  let content_element = document.getElementById( trigger_item.getAttribute('aria-controls') );
  
  if ( content_element ) {
    if ( content_element.classList.contains('accordion__content--expanded') ) {
      trigger_item.setAttribute('aria-expanded', false);
      accordion_content_collapse(content_element);
    } 
    else {
      trigger_item.setAttribute('aria-expanded', true);
      accordion_content_expand(content_element);
    }
  }
}

function accordion_content_collapse(content_element) {
  
  if ( content_element ) {
    content_element.classList.remove('accordion__content--expanded');
  }
}

function accordion_content_expand(content_element) {

  if ( content_element ) {
    content_element.classList.add('accordion__content--expanded');
  }
}
              
            
!
999px

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