function getElementsByXPath(xpath, parent)
{
  let results = [];
  let query = document.evaluate(xpath,
      parent || document,
      null, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
  for (let i=0, length=query.snapshotLength; i<length; ++i) {
    results.push(query.snapshotItem(i));
  }
  return results;
}

getElementsByXPath('/html/body//h2')[0].innerText;
getElementsByXPath('/html/body//h2')[1].innerText;