Regex using groups in javascript

Convert the xml to uppercase except text or textContent and attribute values.

var XML_String="<start_tag><data>some data</data><data id=\"xyz\" id2=\"yyy\">some data2</data></start_tag>"  
XML_String=XML_String.replace(/(<|<\/)([\"_a-zA-Z0-9\s=]*)(>)/gi, function(s, group1, group2,group3) { 
 if(group2.indexOf("\"")>-1){
  var substr=group2;
  substr=substr.replace(/([a-zA-Z0-9=_\s]*)(\")([_a-zA-Z0-9]*)(\")/gi,function(sb,group1,group2,group3,group4){
   return group1.toUpperCase()+group2+group3+group4;
  });
  group2=substr;   
 }else{
  group2=group2.toUpperCase()
 }   
return group1+group2+group3;});