Cloudflare Worker with LaunchDarkly integration

index.js

import { getAssetFromKV } from "@cloudflare/kv-asset-handler";
const { init } = require("launchdarkly-cloudflare-edge-sdk");
let ldClient;

class FlagsStateInjector {
  async element(element) {
    // fetch all flag values for client-side SDKs as evaluated for an anonymous user
    // use a more appropriate user key if needed
    const user = {
      key: "anonymous",
      kind: "user"
    };
    const allFlags = await ldClient.allFlagsState(user, {
      clientSideOnly: true,
    });
    element.append(
      `<script>window.ldFlags = ${JSON.stringify(allFlags)}</script>`,
      { html: true }
    );
  }
}

class H1ElementHandler {
  async element(element) {
    // replace the header text with the value of a string flag
    const headerText = await getFlagValue("header-text");
    element.setInnerContent(headerText);
  }
}
const rewriter = new HTMLRewriter();
rewriter.on("h1", new H1ElementHandler());
rewriter.on("head", new FlagsStateInjector());

addEventListener("fetch", (event) => {
  event.respondWith(handleEvent(event));
});

async function handleEvent(event) {
  let options = {};

  try {
    if (!ldClient) {
      ldClient = init(MY_KV, "MY_KEY");
      await ldClient.waitForInitialization();
    }

    const page = await getAssetFromKV(event, options);

    // allow headers to be altered
    const response = new Response(page.body, page);

    const customHeader = await getFlagValue("custom-response-headers");
    customHeader.headers.forEach((header) => {
      response.headers.set(header.name, header.value);
    });

    return rewriter.transform(response);
  } catch (e) {
    console.log(e);
    return new Response(e.message || e.toString(), { status: 500 });
  }
}