Caching with Cloudflare

cloudflare-cache.js

function isCacheable(response) {
  const vary = response.headers.get('Vary')

  return (
    response.status >= 200 &&
    response.status < 400 &&
    response.status !== 206 &&
    response.headers.get('Cache-Control') != null &&
    vary !== '_' &&
    vary !== '*'
  )
}

// response.body may be a ReadableStream that can only be read once. If so,
// we can't send the same copy to the cache _and_ over the network back to the
// client.
function cloneResponse(response) {
  const { body } = response
  const [body1, body2] = body && typeof body.tee === 'function' ? body.tee() : [body, body]
  return [new Response(body1, response), new Response(body2, response)]
}

// See https://developers.cloudflare.com/workers/reference/apis/cache/
export default async function cacheResponses(request, next) {
  if (request.method !== 'GET') return next(request)

  const cache = caches.default
  const cachedResponse = await cache.match(request)
  if (cachedResponse) return cachedResponse

  const response = await next(request)

  if (!isCacheable(response)) return response

  const [r1, r2] = cloneResponse(response)
  await caches.default.put(request, r1)
  return r2
}