strip-markdown

function stripMarkdown(md?: string, opts?: any) {
  if (!md) {
    return;
  }

  const options = opts || {};
  options.listUnicodeChar = options.listUnicodeChar ? options.listUnicodeChar : false;
  options.stripListLeaders = options.stripListLeaders ? options.stripListLeaders : true;
  options.gfm = options.gfm ? options.gfm : true;
  options.useImgAltText = options.useImgAltText ? options.useImgAltText : true;
  options.abbr = options.abbr ? options.abbr : false;
  options.replaceLinksWithURL = options.replaceLinksWithURL ? options.replaceLinksWithURL : false;
  options.htmlTagsToSkip = options.htmlTagsToSkip ? options.htmlTagsToSkip : [];

  let output = md || '';

  // Remove horizontal rules (stripListHeaders conflict with this rule, which is why it has been moved to the top)
  output = output.replace(/^(-\s*?|\*\s*?|_\s*?){3,}\s*/gm, '');

  try {
    if (options.stripListLeaders) {
      if (options.listUnicodeChar)
        output = output.replace(/^([\s\t]*)([*\-+]|\d+\.)\s+/gm, `${options.listUnicodeChar} $1`);
      else output = output.replace(/^([\s\t]*)([*\-+]|\d+\.)\s+/gm, '$1');
    }
    if (options.gfm) {
      output = output
        // Header
        .replace(/\n={2,}/g, '\n')
        // Fenced codeblocks
        .replace(/~{3}.*\n/g, '')
        // Strikethrough
        .replace(/~~/g, '')
        // Fenced codeblocks
        .replace(/`{3}.*\n/g, '');
    }
    if (options.abbr) {
      // Remove abbreviations
      output = output.replace(/\*\[.*\]:.*\n/, '');
    }
    output = output
      // Remove HTML tags
      .replace(/<[^>]*>/g, '');

    let htmlReplaceRegex = new RegExp('<[^>]*>', 'g');
    if (options.htmlTagsToSkip.length > 0) {
      // Using negative lookahead. Eg. (?!sup|sub) will not match 'sup' and 'sub' tags.
      const joinedHtmlTagsToSkip = `(?!${options.htmlTagsToSkip.join('|')})`;

      // Adding the lookahead literal with the default regex for html. Eg./<(?!sup|sub)[^>]*>/ig
      htmlReplaceRegex = new RegExp(`<${joinedHtmlTagsToSkip}[^>]*>`, 'ig');
    }

    output = output
      // Remove HTML tags
      .replace(htmlReplaceRegex, '')
      // Remove setext-style headers
      .replace(/^[=-]{2,}\s*$/g, '')
      // Remove footnotes?
      .replace(/\[\^.+?\](: .*?$)?/g, '')
      .replace(/\s{0,2}\[.*?\]: .*?$/g, '')
      // Remove images
      .replace(/!\[(.*?)\][[(].*?[\])]/g, options.useImgAltText ? '$1' : '')
      // Remove inline links
      .replace(/\[([^\]]*?)\][[(].*?[\])]/g, options.replaceLinksWithURL ? '$2' : '$1')
      // Remove blockquotes
      .replace(/^\s{0,3}>\s?/gm, '')
      // .replace(/(^|\n)\s{0,3}>\s?/g, '\n\n')
      // Remove reference-style links?
      .replace(/^\s{1,2}\[(.*?)\]: (\S+)( ".*?")?\s*$/g, '')
      // Remove atx-style headers
      .replace(/^(\n)?\s{0,}#{1,6}\s+| {0,}(\n)?\s{0,}#{0,} #{0,}(\n)?\s{0,}$/gm, '$1$2$3')
      // Remove * emphasis
      .replace(/([*]+)(\S)(.*?\S)??\1/g, '$2$3')
      // Remove _ emphasis. Unlike *, _ emphasis gets rendered only if
      //   1. Either there is a whitespace character before opening _ and after closing _.
      //   2. Or _ is at the start/end of the string.
      .replace(/(^|\W)([_]+)(\S)(.*?\S)??\2($|\W)/g, '$1$3$4$5')
      // Remove code blocks
      .replace(/(`{3,})(.*?)\1/gm, '$2')
      // Remove inline code
      .replace(/`(.+?)`/g, '$1')
      // // Replace two or more newlines with exactly two? Not entirely sure this belongs here...
      // .replace(/\n{2,}/g, '\n\n')
      // // Remove newlines in a paragraph
      // .replace(/(\S+)\n\s*(\S+)/g, '$1 $2')
      // Replace strike through
      .replace(/~(.*?)~/g, '$1');
  } catch (e) {
    console.error(e);

    return md;
  }

  return output;
}