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Function: initLogger()

initLogger(cb?, spec?): void
Defined in: index.d.ts:1286 Initialize the logger. You usually don’t need to call this. The package’s main entry (wrapped.js) calls initLogger() with no arguments on first evaluation, so simply import '@simular-ai/simulang-js' is enough to see [level] message records on stderr. Call this directly only when you want to override that default — to forward records to a JS callback, change the filter spec, or silence everything.
  • No callback (initLogger() or initLogger(null, spec)): records are formatted as [level] message and written to stderr.
  • With a callback (initLogger(cb, spec)): records are forwarded to the JS callback via a non-blocking, unref’d threadsafe function. Use this for GUI panels, file appenders, or routing through a logging library like pino. The unref’d dispatch means the logger does not keep the Node event loop alive on its own.
Omit spec to read RUST_LOG (falls back to "simulang_rs=info,warn" when RUST_LOG is unset — info-level records from simulang’s own actions, warn-level from every other crate). Pass an explicit spec to override RUST_LOG. Syntax is identical to RUST_LOG:
  • "info" — global level
  • "simulang_rs=debug,warn" — per-module override + default
  • "simulang_rs::windows=trace,simulang_rs::macos=debug,warn" — multiple
  • "off" — disable all logging
Safe to call repeatedly: each call atomically swaps the inner sink and filter — useful for e.g. starting on stderr at boot and switching to a renderer callback once the UI is ready. Don’t log from inside the callback. Whether directly (console.log is fine — that’s not a log::*! call) or transitively via another simulang-js function whose Rust side emits a record, you’d feed the relay another record, which queues another callback invocation, and so on forever. The callback itself runs on the Node main thread; the non-blocking dispatch from Rust is what creates the recursion risk.

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Parameters

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cb?

((arg) => unknown) | null

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spec?

string | null

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Returns

void