/**
 * div.js-show-hide
 *   div.js-show-hide-toggle
 *     toggle here
 *   div
 *     content here
 */

document.addEventListener('DOMContentLoaded', function() {

  var elements = Array.from(document.querySelectorAll('.js-show-hide-toggle')),
      toggles = [];

  function addEventHandler(el) {
    el.addEventListener('click', function elClickListener() {
      var toggle = toggles[el.dataset.index];
      toggle.collapsed = !toggle.collapsed;
      toggle.parent.classList.toggle('collapsed', toggle.collapsed);
    });
  }

  elements.forEach(function(el, i) {
    var target = el.nextElementSibling;
    el.dataset.index = i;
    var coll = el.parentElement.classList.contains('collapsed');
    target.classList.add('js-show-hide-target');
    toggles.push({index: i, target: target, collapsed: coll, parent: el.parentElement});
    addEventHandler(el);
  });
});