function stringToSlug(str) {
  // remove accents
  var from = "àáãảạăằắẳẵặâầấẩẫậèéẻẽẹêềếểễệđùúủũụưừứửữựòóỏõọôồốổỗộơờớởỡợìíỉĩịäëïîöüûñçýỳỹỵỷ",
      to   = "aaaaaaaaaaaaaaaaaeeeeeeeeeeeduuuuuuuuuuuoooooooooooooooooiiiiiaeiiouuncyyyyy";
  for (var i=0, l=from.length ; i < l ; i++) {
    str = str.replace(RegExp(from[i], "gi"), to[i]);
  }

  str = str.toLowerCase()
        .trim()
        .replace(/[^a-z0-9\-]/g, '-')
        .replace(/-+/g, '-');

  return str;
}