cfdeploy.yml

name: Deploy Cloudflare Worker for All Github Environments

on:
  push:
    branches:
      - main

jobs:
  deploy-production-default:
    runs-on: ubuntu-latest
    name: Build and Deploy To Cloudflare
    steps:
      - uses: actions/checkout@v3
      - name: Run npm install
        run: npm install
      - name: Publishing Worker for Github Environment ProdDefault
        uses: cloudflare/wrangler-action@2.0.0
        with:
          apiToken: ${{ secrets.CF_API_TOKEN }}
          accountId: ${{ secrets.CF_ACCOUNT_ID }}
          command: publish --env proddefault

index.ts

export interface Env {
  START_PATH: string;
  TARGET_URL: string;
}

export default {
  async fetch(
    request: Request,
    env: Env,
    ctx: ExecutionContext
  ): Promise<Response> {
      const url = new URL(request.url)

      if (url.pathname.startsWith(env.START_PATH)) {
        return fetch(
          getTargetURL(env, url),
          request
        )
      }

      return fetch(request)
   },
};


function getTargetURL (env: Env, currentURL: URL): string {
  const targetURL = new URL(env.TARGET_URL)
  targetURL.pathname = currentURL.pathname
  return targetURL.toString()
}