Simple slide toggle with pure javascript

by Cam Gould

HTML

<button id="toggleButton">Click to slideDown!</button>
<div id="toggleElement">
  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.
</div>

CSS

#toggleElement {
  transition: height 0.3s ease-out;
  height: 0;
  overflow: hidden;
}

/* Demo styles */
* {
  font-family: sans-serif;
  box-sizing: border-box;
}

#toggleElement {
  max-width: 400px;
}

JavaScript

var toggleTrigger = document.getElementById('toggleButton'),
      toggleElement = document.getElementById('toggleElement');

  toggleTrigger.addEventListener('click', function (e) {
    e.preventDefault();
    var toggleElementHeight = toggleElement.scrollHeight;

    if (toggleElement.classList.contains('visible')) {
      toggleElement.style.height = '0px';
      toggleElement.className = '';
    } else {
      toggleElement.style.height = toggleElementHeight + 'px';
      toggleElement.className = 'visible';
    }
  });