Advanced

These chapters go deeper into how Jco binds components to JavaScript. They assume familiarity with the Transpiling chapter and the WASI support section.

• Optimized Host Bindings: the fast paths Jco generates for host calls, and when they apply.
• WIT Type representations: how each WIT type appears in JavaScript.
• Manual Wasm instantiation with WASI overrides: instantiating a transpiled component yourself and replacing individual WASI interfaces.
• Detecting traps: telling a component trap apart from an ordinary error.
• Preview 3 streams and backpressure: how WASI 0.3 streams flow between host and guest.
• Preview 3 host value disposal: what happens to host-provided values a guest discards.