function filterChildren(el, nodeName, single) {
  var result = [];
  var childNodes = el.childNodes;

  for (var i = 0; i < childNodes.length; i++) {
    let node = childNodes[i];

    if (node.nodeType === 1 && node.nodeName.toLowerCase() === nodeName) {
      if (single) {
        return node;
      } else {
        result.push(node);
      }
    }
  }

  if (!single) {
    return result;
  }
}
Find all direct decendents of a specific type
@param {element} el
@param {string} nodeName
@param {boolean} [single]
@returns {element[]} children
@memberof Core