Implementation using Firebase

Implementation of a basic CORS-Anywhere server is very straightforward. Simply do the following:

1. Fork this repository.
2. Within index.js, replace the website URLs in the originWhitelist array with the web address(es) that you want to authorise. You can keep the first string here as is for local testing (assuming you're using port 3000).
3. Navigate to the functions directory from the terminal and run npm install.
4. Create a new Firebase account if you don't already have one.
5. Install the Firebase CLI by running npm install -g firebase-tools.
6. Log into Firebase using your Google account credentials with firebase login in the terminal.
7. From the Firebase console in your browser, create a new project. Give it a name and project-id.
8. Replace the value of the default field in .firebaserc with your project-id.
9. From the bottom-left of the Firebase browser console, upgrade your billing plan from Spark (free) to Blaze (paid). Don't worry though, so long as you don't operate an open proxy or make a huge amount of requests it should be fine. You should also set up billing alerts and a cutoff just to be sure. There is a generous free tier of 2 million cloud function invocations per month in any case.
10. From the terminal, navigate to the functions directory and npm run deploy. My function deployed to https://proxy-ibmasyzzya-uc.a.run.app.
11. Prepend the API request in your application code with this URL like so. That's it, you've implemented the server!