See https://github.com/mochokidae/OpenHeart

worker.js

addEventListener('fetch', event => {
  event.respondWith(handleRequest(event.request))
})

async function handleRequest(request) {
  if (request.method !== 'POST') return

  const url = new URL(request.url)
  const id = url.searchParams.get('id')
  const emoji = ensureEmoji(await request.text())

  if (!id || !emoji) return new Response('not ok', {status: 500})

  const key = `${id}:${emoji}`

  // https://developers.cloudflare.com/workers/runtime-apis/kv/
  const currentCount = Number(await(NAMESPACE.get(key)) || 0)
  await NAMESPACE.put(key, currentCount + 1)

  return new Response('ok')
}

function ensureEmoji(emoji) {
  const segments = Array.from(new Intl.Segmenter({ granularity: 'grapheme' }).segment(emoji.trim()))
  const parsedEmoji = segments.length > 0 ? segments[0].segment : null
  
  if (/\p{Emoji}/u.test(parsedEmoji)) return parsedEmoji
}