Vanilla JS Table row toggle

table-row-toggle.js

function getClosest(elem, selector) {
  var firstChar = selector.charAt(0);
  for (; elem && elem !== document; elem = elem.parentNode) {
      if (firstChar === '.') {
          if (elem.classList.contains(selector.substr(1))) {
              return elem;
          }
      }
      if (firstChar === '#') {
          if (elem.id === selector.substr(1)) {
              return elem;
          }
      }
      if (firstChar === '[') {
          if (elem.hasAttribute(selector.substr(1, selector.length - 2))) {
              return elem;
          }
      }
      if (elem.tagName.toLowerCase() === selector) {
          return elem;
      }
  }
  return false;
};

function ready(fn) {
  if (document.readyState != 'loading') {
      fn();
  } else {
      document.addEventListener('DOMContentLoaded', fn);
  }
}

ready(function () {
  var elements = document.querySelectorAll('.expand-json');
  for (var i = 0; i < elements.length; i++) {
      var el = elements[i];
      el.addEventListener('click', function (event) {
          var tr = getClosest(event.target, 'tr');
          var nexttr = tr.nextElementSibling;
          if (nexttr.style.display === 'none') {
              nexttr.style.display = '';
          } else {
              nexttr.style.display = 'none';
          }
      });
  }
});