code: function showInvisibles(str) {
    let ret = '';
    for (let i = 0; i < str.length; i++) {
      switch (str[i]) {
        case ' ':
          ret += '·'; // Middle Dot, \u00B7
          break;
        case '\n':
          ret += '⏎'; // Return Symbol, \u23ce
          break;
        case '\t':
          ret += '↹'; // Left Arrow To Bar Over Right Arrow To Bar, \u21b9
          break;
        case '\r':
          ret += '␍'; // Carriage Return Symbol, \u240D
          break;
        default:
          ret += str[i];
          break;
      }
    }
    return ret;
  }
docs: Converts invisible characters to a commonly recognizable visible form.
  @param {string} str - The string with invisibles to convert.
  @returns {string} The converted string.