Use Cases

qzjs is a WinterTC-compatible runtime for embedding JS (and WebAssembly) inside C applications, with a thread-safe JSON message boundary and minimal overhead. It shines wherever you want to push logic into JavaScript without standing up a heavy process or a full browser engine.

Embedded & Edge Nodes

The defining case: run JS on resource-constrained targets.

• Edge gateways — devices that need to interpret rules, filters, or protocol glue written in JS, reloadable without recompiling the C firmware.
• Embedded devices — qzrt's zero-dependency build (2.45 MiB stripped, ~5 ms startup) fits on targets where Node/Deno cannot.
• Low-overhead scripting — a single initial_script or a message-driven handler replaces a hand-written C state machine.

The host stays in C; JS runs on qzjs's own internal thread with its own libuv loop.

Extending a C Application with Scripting

Give your C app a scripting surface without a full interpreter integration.

• Ship logic as initial_script so it can be updated at runtime.
• Drive the runtime over JSON messages — your app's domain events become JS handler calls, and JS results flow back through message_cb.
• Expose your C functions to JS through a compiled-in extension (Examples, extension/).

WinterTC Web APIs on Native

Code written against standard Web APIs runs as-is:

• fetch, WebSocket, EventSource, streams, timers, crypto.subtle, BroadcastChannel, serve() (HTTP/WS/gRPC) — all available as globals.

Parallelism at the Edge

• new Worker(url) runs isolated contexts — as parallel threads or, under the default -DQZ_PROCESS_MODEL=ISOLATED, as dedicated child processes.
• Offload CPU-heavy or blocking work from the main runtime thread.