EXT 错误 对象不支持“createContextualFragment”属性或方法

<script type="text/javascript">
if ((typeof Range !== "undefined") && !Range.prototype.createContextualFragment)
{
Range.prototype.createContextualFragment = function(html)
{
var frag = document.createDocumentFragment(),
div = document.createElement("div");
frag.appendChild(div);
div.outerHTML = html;
return frag;
};
}
</script>