old_contents: /* Convert the characters &, <, >, " (double quote), and ' (apostrophe), in a string to their corresponding HTML entities. */
  
  function convertHTML(str) {
    // &colon;&rpar;
    return str;
  }
  
  convertHTML("Dolce & Gabbana");
  
new_contents: /* Convert the characters &, <, >, " (double quote),
   and ' (apostrophe), in a string to their corresponding HTML entities. */
  
  function convertHTML(str) {
    return str.split('')
      .map(char => { 
        switch(char) {
          case '&':
            return '&amp;';
          case '<':
            return '&lt;';
          case '>':
            return '&gt;';
          case '"':
            return '&quot;';
          case "'":
            return '&apos;';
          default:
            return char;
        }})
      .join('');
  }
  
  console.log(convertHTML("Dolce & Gabbana"));
  
subject: add convertHTML