Generating a footnote from selected text

Question

I am trying to script InDesign using ExtendScript. I want the script to cut the selected text, insert a footnote and paste the text into the footnote body. What I have tried:

 function makeFootnoteOfSelection(){
   var fnText = app.activeDocument.selection[0];
         // this should actually clone the selected text, not reference it, because the next statement zaps it from memory
   app.activeDocument.selection[0].remove();  // works
   var fNote = app.activeDocument.selection[0].footnotes.add();  // works, adds an empty footnote with a reference
   fNote.contents = fnText.contents;
         // this replaces the reference number, I was hoping to retain it and just add the text
         // fNote.contents += fnText.contents; also replaces the reference number
}