var parent = document.getElementById('parent');
for(var i = 0; i < 10000; i++) {
 var child = document.createElement('div');
 var text = document.createTextNode('' + i);
 child.appendChild(text);
 parent.appendChild(child);
}

var i = 0, max = 10000;
setTimeout(function addNodes() {
 for(var step = i + 500; i < step; i++) {
  var child = document.createElement('div');
  child.appendChild(document.createTextNode('' + i));
  div.appendChild(child);
 }
 if(i < max) {
  setTimeout(addNodes, 0);
 }
}, 0);

var parent = document.getElementById('parent');
var div = document.createElement('div');
for(var i = 0; i < 10000; i++) {
 var child = document.createElement('div');
 var text = document.createTextNode('' + i);
 child.appendChild(text);
 div.appendChild(child);
}
parent.appendChild(div);

var parent = document.getElementById('parent');
var frag = document.createDocumentFragment();
for(var i = 0; i < 10000; i++) {
 var child = document.createElement('div');
 var text = document.createTextNode('' + i);
 child.appendChild(text);
 frag.appendChild(child);
}
parent.appendChild(frag);

var div = document.createElement('div');
div.innerHTML = '<th>xxx</th>';
console.log(div);

<div>xxx</div>

<div><th>xxx</th></div>

var node = document.createElement('div');
node.innerHTML = '<table><tbody><tr><th>xxx</th></tr></tbody></table>';
// 把外面的几层皮扒掉就是想要的 th 了
var depth = 3;
while(depth--) {
 node = node.lastChild;
 }
console.log(node.firstChild);

// 需要单独处理的一些特殊节点
var map = {
 legend : [1, '<fieldset>', '</fieldset>'],
 tr : [2, '<table><tbody>', '</tbody></table>'],
 col : [2, '<table><tbody></tbody><colgroup>', '</colgroup></table>'],

 _default : [0, '', '']
};
map.td = map.th = [3, '<table><tbody><tr>', '</tr></tbody></table>'];
map.option = map.optgroup = [1, '<select multiple="multiple">', '</select>'];
map.thead = map.tbody = map.colgroup = map.caption = map.tfoot = [1, '<table>', '</table>']
map.text = map.circle = map.ellipse = map.line = map.path = map.polygon = map.polyline = map.rect = [1, '<svg xmlns="http://www.w3.org/2000/svg" version="1.1">','</svg>'];

var TAG_RE = /<([\w:]+)/;

module.exports = function(templateString) {
 var frag = document.createDocumentFragment(),
  m = TAG_RE.exec(templateString);
 // 单纯字符串的情况
 if(!m) {
  frag.appendChild(document.createTextNode(templateString);
  return frag;
 }

 var tag = m[1],
  wrap = map[tag] || map._default,
  depth = wrap[0],
  prefix = wrap[1],
  suffix = wrap[2],
  node = document.createElement('div');
 // 拼接节点字符串
 node.innerHTML = prefix + templateString.trim() + suffix;
 // 去除外包裹层，只留字符串转化的节点
 while(depth--) node = node.lastChild;
 // 只有一个节点的情况
 if(node.firstChild === node.lastChild) { 
  frag.appendChild(node.firstChild);
  return frag;
 }
 // 多个节点，依序添加到 frag
 var child;
 while(child = node.firstChild) {
  frag.appendChild(child);
 }
 return frag;
}