Нужна функция для преобразования Slack Markdown в HTML

Если кто ищет что-то подобное - вот решение

function slackMarkdownToHtml(markdown) {
  // Replace asterisks with bold tags
  let html = markdown.replace(/\*(.+?)\*/g, '<b>$1</b>');

  // Replace underscores with italic tags
  html = html.replace(/\_(.+?)\_/g, '<i>$1</i>');

  // Replace tildes with strike-through tags
  html = html.replace(/\~(.+?)\~/g, '<s>$1</s>');

  // Replace dashes with unordered list items
  html = html.replace(/- (.*)/g, '<li>$1</li>');
  html = html.replace(/\n-/g, '\n</ul><ul>-')
  html = '<ul>' + html + '</ul>';

  // Replace numbers with ordered list items
  html = html.replace(/[0-9]\. (.*)/g, '<li>$1</li>');
  html = html.replace(/\n[0-9]\./g, '\n</ol><ol>$&')
  html = '<ol>' + html + '</ol>';

  // Replace Slack's link syntax with anchor tags
  html = html.replace(/\[(.+?)\]\((.+?)\)/g, '<a href = "$2">$1</a>');

  return html;
}

И наоборот — HTML в Slack Markdown

function htmlToSlackMarkdown(html) {
  // Replace newline characters with a line break
  let markdown = html.replace(/\n/g, '\n\n');

  // Replace bold tags with asterisks
  markdown = markdown.replace(/<b>/g, '*').replace(/</b>/g, '*');

  // Replace italic tags with underscores
  markdown = markdown.replace(/<i>/g, '_').replace(/</i>/g, '_');

  // Replace strike-through tags with tildes
  markdown = markdown.replace(/<s>/g, '~').replace(/</s>/g, '~');

  // Replace unordered list items with dashes
  markdown = markdown.replace(/<li>/g, '- ').replace(/</li>/g, '');

  // Replace ordered list items with numbers
  markdown = markdown.replace(/<ol>/g, '').replace(/</ol>/g, '');
  markdown = markdown.replace(/<li>/g, '1. ').replace(/</li>/g, '');
  markdown = markdown.replace(/\n1\./g, '\n2.');
  markdown = markdown.replace(/\n2\./g, '\n3.');
  markdown = markdown.replace(/\n3\./g, '\n4.');
  markdown = markdown.replace(/\n4\./g, '\n5.');
  markdown = markdown.replace(/\n5\./g, '\n6.');
  markdown = markdown.replace(/\n6\./g, '\n7.');
  markdown = markdown.replace(/\n7\./g, '\n8.');
  markdown = markdown.replace(/\n8\./g, '\n9.');
  markdown = markdown.replace(/\n9\./g, '\n10.');

  // Replace anchor tags with Slack's link syntax
  markdown = markdown.replace(/<a href = "(.+?)">(.+?)</a>/g, '[$2]($1)');

  return markdown;
}