bigbuffet-rw/app/soapbox/utils/rich_content.js

// Returns `true` if the node contains only emojis, up to a limit
export const onlyEmoji = (node, limit = 1, ignoreMentions = true) => {
  if (!node) return false;

  // Remove mentions before checking content
  if (ignoreMentions) {
    node = node.cloneNode(true);
    node.querySelectorAll('a.mention').forEach(m => m.parentNode.removeChild(m));
  }

  if (node.textContent.replaceAll(' ', '') !== '') return false;
  const emojis = Array.from(node.querySelectorAll('img.emojione'));
  if (emojis.length === 0) return false;
  if (emojis.length > limit) return false;
  const images = Array.from(node.querySelectorAll('img'));
  if (images.length > emojis.length) return false;
  return true;
};