How to get the speical character in acrobat by JS ?

How to get the speical character and output  txt  in acrobat by JS ?

example:  ® ™ è

I can get them,

but why the ™ have lost when I save these character to txt,?

function getword2(doc){

  var i, j, ckWord, numWords, aWords = [];

  for (i = 0; i < doc.numPages; i++ ) {

  var bWords = [];

  numWords = doc.getPageNumWords(i);

  for (j = 0; j < numWords; j++) {

  ckWord = doc.getPageNthWord(i, j, false);

  if (ckWord) {

  bWords.push(ckWord);  // Add word to array

  }

  }

  aWords.push( bWords );

  }

  return aWords.join('\r\n');

}

function output_csv2(){

  var outputString = getword2(this);

  this.createDataObject("output.txt", outputString); 

  this.exportDataObject({ cName:"output.txt", nLaunch: "2"});

}