Introduction

webview-bridge-kit is a bridge for passing messages, type-safely, between a web app running inside a WebView and the React Native host that wraps it.

Both sides share a single contract, so message names, payloads, and response types line up at compile time — and, if you attach schemas, they are validated at runtime too. It's a thin RPC + pub/sub layer on top of the WebView's postMessage / injectJavaScript.

The three message kinds

The bridge deals with exactly three kinds of messages.

Kind	Direction	Reply	Use for
request	web → native	yes	Calls that need a response (login, fetch a token)
command	web → native	no	Fire-and-forget orders (open a screen, send a log)
event	native → web	no	Notifications pushed from native (deep links, app state)

• request returns a Promise that resolves with the native handler's return value.
• command is fire-and-forget. You send it and move on.
• event is pushed from native to web. The web side subscribes to receive them.

Next, define these in a contract, then see how to use them in React and React Native.