changke/rss-cors-proxy-deno

A CORS proxy server for fetching RSS sources written in Deno, can be used with Deno Deploy.

RSS CORS Proxy

A CORS proxy server for fetching RSS sources written in Deno, can be used with Deno Deploy.

Why

It is relatively easy to parse RSS in browser because there is the DOMParser API.

So one can try write an RSS reader in JS that runs on localhost.

But most RSS sources cannot be simply fetched locally because of CORS policy.

One workaround would be a proxy server that retrieves RSS sources and adds CORS header to allow local consuming.

┌───────┐        ┌─────┐    ┌──────┐
│Browser│        │Proxy│    │Target│
└───┬───┘        └──┬──┘    └──┬───┘
    │               │          │    
    │ CORS fetch()  │          │    
    │──────────────>│          │    
    │               │          │    
    │               │ fetch()  │    
    │               │─────────>│    
    │               │          │    
    │               │Response()│    
    │               │<─────────│    
    │               │          │    
    │CORS Response()│          │    
    │<──────────────│          │    
┌───┴───┐        ┌──┴──┐    ┌──┴───┐
│Browser│        │Proxy│    │Target│
└───────┘        └─────┘    └──────┘

There is no stable native fetch API in Node.js LTS yet, but Deno has. And like Node, only a few lines are needed to start a webserver in Deno.

This project takes a target RSS feed URL, fetches the content and sends to response with added CORS header.

Inspired by this repo.

How

You need to deploy this code on a server that runs Deno.

The easiest way would be to use Deno Deploy. Create a new playground, paste the code and deploy.

To use, visit https://[your-deploy-id].deno.dev/?target=RSS_URL, and make sure "RSS_URL" is encoded with encodeURIComponent().

Example: to fetch https://hnrss.org/frontpage locally:

1. Encode the URL to https%3A%2F%2Fhnrss.org%2Ffrontpage.
2. Visit https://[your-deploy-id].deno.dev/?target=https%3A%2F%2Fhnrss.org%2Ffrontpage to get the proxy-ed response.