getMarkupWrap困惑

#1

react/lib/getMarkupWrap.js 中 dummyNode.innerHTML = ‘’; //意义何在？好像没有地方用到嘛

function getMarkupWrap(nodeName) {
  ("production" !== process.env.NODE_ENV ? invariant(!!dummyNode, 'Markup wrapping node not initialized') : invariant(!!dummyNode));
  if (!markupWrap.hasOwnProperty(nodeName)) {
    nodeName = '*';
  }
  if (!shouldWrap.hasOwnProperty(nodeName)) {
    if (nodeName === '*') {
      dummyNode.innerHTML = '<link />';
    } else {
      dummyNode.innerHTML = '<' + nodeName + '></' + nodeName + '>';
    }
    shouldWrap[nodeName] = !dummyNode.firstChild;
  }
  return shouldWrap[nodeName] ? markupWrap[nodeName] : null;
}