JSFiddle - React, Tailwind, and code Playground

by moshfeu

HTML

<button id="trigger">
	Drop It
</button>
<br><br>
<div class="content">
  <p class="no-margin"><strong>This content is revealed by a dropdown.</strong> Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</p>
</div>

CSS

.content{
	display: none;
	position: relative;
	padding: 1rem 1.5rem;
	border: 1px solid #000;
	border-radius: 5px;
  box-sizing: border-box;
}

JavaScript

function slideDown(el, duration = 500){
  // momentarily show element to calculate dimensions
  Object.assign(el.style, {
    position: 'absolute',
    display: 'block',
    visibility: 'hidden',
    height: 'auto',
    overflow: 'hidden'
  });

  const elHeight = el.offsetHeight;
  el.style.removeProperty('position');
  el.style.removeProperty('visibility');
  el.style.height = '0px';
  console.log(elHeight);

  el.animate([
    { height: '0px' },
    { height: elHeight+'px' }
  ], {
    duration: duration,
    fill: 'forwards'
  });
  setTimeout(function() {
    el.style.removeProperty('height');
    el.style.removeProperty('overflow');
  }, duration);
}

function slideUp(el, duration = 500){
  el.style.overflow = 'hidden';
  console.log(el.offsetHeight);

  const animation = el.animate([
    { height: el.offsetHeight+'px' },
    { height: '0px' }
  ], {
    duration: duration,
    fill: 'forwards'
  });
  setTimeout(function() { // callback not yet supported enough
    el.style.removeProperty('height');
    el.style.removeProperty('overflow');
    el.style.display = 'none';
    animation.cancel();
  }, duration);
}

const button = document.getElementById('trigger'),
  content = document.querySelector('.content');

button.addEventListener('click', function(){
  if(this.classList.contains('active')){
    this.classList.remove('active');
		this.textContent = 'Drop It';
    slideUp(content);
  } else {
    this.classList.add('active');
		this.textContent = 'Retract It';
    slideDown(content);
  }
});