How to Clear Text formatting by script?

Could it be the influence of paragraph styles? I also changed paragraph style settings to revert to default.

/**
  * @File make selected text default attributes
  * @version 1.1.0
  * @7111211 sttk3.com
  * @7340357 © 2023 sttk3.com
*/

(function() {
  if(app.documents.length <= 0) {return ;}
  var doc = app.documents[0] ;
  
  // get selected text
  var targetRanges = getTextSelection() ;
  var targetRangeLength = targetRanges.length ;
  if(targetRangeLength <= 0) {return ;}

  // get [Normal Character Style], [Normal Paragraph Style]
  var defaultCharacterStyle = doc.characterStyles[0] ;
  var defaultParagraphStyle = doc.paragraphStyles[0] ;

  // reset text style
  for(var i = 0 ; i < targetRangeLength ; i++) {
    var currentRange = targetRanges[i] ;
    defaultCharacterStyle.applyTo(currentRange, true) ;
    defaultParagraphStyle.applyTo(currentRange, true) ;
  }
})() ;

/**
  * returns selection as an Array of TextRange
  * @Returns {Array<TextRange>}
*/
function getTextSelection() {
  var sel = app.selection ;
  var selLength = sel.length ;
  var res = [] ;
  
  switch(sel.constructor.name) {
    case 'Array' :
      if(!sel[0]) {return res ;}
      for(var i = 0 ; i < selLength ; i++) {
        var itemType = sel[i].constructor.name ;
        if(itemType == 'TextFrame') {
          res.push(sel[i].textRange) ;
        } else if(itemType == 'TextRange') {
          res.push(sel[i]) ;
        }
      }
      break ;
    case 'TextRange' :
      res.push(sel) ;
      break ;
  }
  return res ;
}