+var sortOrder;
+
+if ( document.documentElement.compareDocumentPosition ) {
+ sortOrder = function( a, b ) {
+ var ret = a.compareDocumentPosition(b) & 4 ? -1 : a === b ? 0 : 1;
+ if ( ret === 0 ) {
+ hasDuplicate = true;
+ }
+ return ret;
+ };
+} else if ( Array.prototype.indexOf ) {
+ var indexOf = Array.prototype.indexOf,
+ allSort = document.getElementsByTagName("*");
+
+ sortOrder = function( a, b ) {
+ var ret = indexOf.call( allSort, a ) - indexOf.call( allSort, b );
+ if ( ret === 0 ) {
+ hasDuplicate = true;
+ }
+ return ret;
+ };
+} else if ( "sourceIndex" in document.documentElement ) {
+ sortOrder = function( a, b ) {
+ var ret = a.sourceIndex - b.sourceIndex;
+ if ( ret === 0 ) {
+ hasDuplicate = true;
+ }
+ return ret;
+ };
+}
+