Fragmented native channels
Android WebMessagePort, iOS WKScriptMessageHandler, Flutter JS channels, HarmonyOS ArkWeb — every platform speaks a different dialect of JS-Native messaging.
Multi-platform JS-Native bridge
One protocol.
Four platforms.
One message protocol, one session model, and one set of WebAssets — running on Android, iOS, Flutter and HarmonyOS. Not a shared runtime: a shared contract.
Android·
iOS·
Flutter·
HarmonyOS
The problem
No session or handshake
Ad-hoc bridges lack a handshake, session lifecycle and cancellation semantics — every H5 page reinvents its own transport.
Security logic scattered
Origin checks, method whitelists and session validation end up duplicated and inconsistent across platforms and pages.
Four implementations, four behaviors
Without a common contract, each platform re-implements the bridge — and each drifted implementation raises integration costs.
The JsBridge2 answer
01
Protocol v1
A single message envelope — request / response / event — with handshake, session, timeout and scope cancellation defined once, in the spec.
02
Security policy chain
A fixed evaluation order: shape → handshake gate → origin → method gate → session → host policies. Hosts extend, never override.
03
Shared WebAssets
One jsbridge-sdk.js bundle runs identically in all four native shells. One source of truth, synced to every platform.
The goal is cross-platform protocol consistency — not a shared runtime.
Three layered tiers
Tier 3 — extensions
lifecycle · registry · system adapters
Tier 2 — JsBridge
session · policies · handshake
Tier 1 — CoreBridge
pure protocol dispatch · handlers · transport
api
BridgeMessage · BridgeError · contracts
Unidirectional dependencies: JsBridge → CoreBridge → api. CoreBridge has zero security dependencies; security has zero core dependencies.
Four platforms, one contract
Android
Java 8 · gradle
Reference implementation. js-bridge-core + WebView transport adapter.
Read integration guide →iOS
Swift 6 · SPM
Swift Package with Bridge core plus a WKWebView transport in BridgeSystem.
Read integration guide →Flutter
Dart 3 · pub
Core package plus host-app example. Transport injected via bindTransport().
Read integration guide →HarmonyOS
ArkTS · HAR
Stage-model HAR core with the same envelope, handshake and policy chain.
Read integration guide →Quick start
Build the JS SDK and sync it to all four platforms first
git clone https://github.com/xesam/JsBridge2.git
cd JsBridge2
cd web-assets && pnpm install && pnpm sync && cd ..
Then load the SDK from any WebView page
<script src="./jsbridge-sdk.js"></script>
const client = createJsBridgeClient({ origin, pageInstanceId })