index.js

module.exports = function markdownItBidi(md) {
  const rules = [
    'heading_open',
    'blockquote_open',
    'paragraph_open',
    'bullet_list_open',
    'ordered_list_open',
    'table_open',
    'th_open',
    'td_open'
  ];

  const bidi = defaultRenderer => (tokens, idx, opts, env, self) => {
    const token = tokens[idx];
    const prevToken = tokens[idx - 1];
    if (token.type === 'th_open' && prevToken.type === 'tr_open') {
      return defaultRenderer(tokens, idx, opts, env, self);
    }
    // omit this token if this is the first child of an element
    if (prevToken && rules.includes(prevToken.type) && token.level > prevToken.level) {
      return defaultRenderer(tokens, idx, opts, env, self);
    }
    token.attrSet('dir', 'auto');
    return defaultRenderer(tokens, idx, opts, env, self);
  };

  const proxy = (tokens, idx, opts, _, self) => {
    return self.renderToken(tokens, idx, opts);
  };

  rules.forEach(rule => {
    const defaultRenderer = md.renderer.rules[rule] || proxy;
    md.renderer.rules[rule] = bidi(defaultRenderer);
  });
};