This is a local first todo app that stores data locally with RxDB and replicates it peer-to-peer with WebRTC to other devices without sending the data through any central server. Open this url in another browser/device/tab to test the replication:
The whole app is implemented without a framework in about 200 lines of TypeScript code. To learn more about how it works, I recommend looking at the source code and read the RxDB Quickstart Guide.