Cloudflare Worker to normalise URLs for cache efficiency

uniform-urls.js

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

/**
 * Fetch request after making casing of hash prefix uniform
 * @param {Request} request
 */
async function handleRequest(request) {
      
  if(request.method === 'OPTIONS') {
    let responseHeaders = setCorsHeaders(new Headers())
    return new Response('', {headers:responseHeaders})
  }

  const url = new URL(request.url);

  if (!url.pathname.startsWith("/range/")) {
    const response = await fetch(request)
    return response;
  }

  const prefix = url.pathname.substr(7);
  const newRequest = "https://api.pwnedpasswords.com/range/" + prefix.toUpperCase()

  if (prefix === prefix.toUpperCase()) {
    const response = await fetch(request, { cf: { cacheKey: newRequest } })
    return response;
  }

  const init = {
      method: request.method,
      headers: request.headers
  }
  
  const modifiedRequest = new Request(newRequest, init)
  const response = await fetch(modifiedRequest, { cf: { cacheKey: newRequest } })
  return response
}

function setCorsHeaders(headers) {
    headers.set('Access-Control-Allow-Origin', '*')
    headers.set('Access-Control-Allow-Methods', 'GET')
    headers.set('Access-Control-Allow-Headers', 'access-control-allow-headers')
    headers.set('Access-Control-Max-Age', 1728000)
    return headers
}