sample.jsx change pdf filename if already exists

ind_dont_overwrite_pdf.jsx

//@target "InDesign"

var increase_or_suffix = function (filename, suffix) {
  if (suffix == undefined) {
    var reg = new RegExp('(\\d+)(\\..+$)');
    var ret = filename.replace(reg, function (m) {
      var mm = m.match(reg);
      if(mm) {
        return (mm[1] * 1 + 1) + mm[2]
      }
    })
    return ret;
  }
  else {
    var reg = new RegExp('(.+)(\\..+$)');
    var ret = filename.replace(reg, function (m) {
      var mm = m.match(reg);
      if (mm) {
        return mm[1] + suffix + mm[2]
      }
    })
    return ret;
  }
}

var increase_filename = function (path, suffix) {
  if (File(path).exists) {
    path_fix = increase_or_suffix(path);
    if (path_fix !== path) {
      path = path_fix;
    }
    else {
      path_fix = increase_or_suffix(path, suffix);
      if (path_fix) {
        path = path_fix;
      }
    }
    return path
  }
  return path
}


var doc = app.documents[0];
var story = doc.stories[0];
var export_path = "~/Desktop/dont.pdf";
for (var i=0, len=story.paragraphs.length; i < len ; i++) {
  export_path = increase_filename(export_path, "-copy1");
  doc.exportFile(ExportFormat.PDF_TYPE, File(export_path));
};