Loggily

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LoggilyDebugs, logs, and spans — one API

Clarity without the clutter. One namespace tree. One output pipeline. One ?. pattern for near-zero overhead. Pure TypeScript. ~3KB. Zero dependencies.

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Near-Zero Cost via ?.

Optional chaining skips the entire call — including argument evaluation — when a level is disabled. ~22x faster than a conventional noop logger in benchmarks.

Structured Logs + Spans

Colorized console in dev, structured JSON in production — same code. Spans with parent-child tracking and trace IDs. Namespace filtering (DEBUG=myapp:db). One import, one config.

OpenTelemetry Bridge

toOtel() stage forwards events to any OTLP backend (Jaeger, Grafana, Datadog). Transparent — events pass through to your other pipeline destinations too.

Pino Transport Compatible

Writable sinks with objectMode receive raw Event objects. Use any Pino transport as a pipeline destination. DEBUG= patterns compatible with the debug package.

Worker Threads + Metrics

Pipeline-based worker logging via postMessage. Span metrics with p50/p95/p99 aggregation. Async context propagation via AsyncLocalStorage.

Composable, Unified

One pipeline replaces debug + JSON logger + tracing SDK. Extend with pipe(baseCreateLogger, withSpans(), myPlugin()). Config arrays for branching: objects configure, arrays branch, values write.

~3KB, Zero Dependencies

Pure TypeScript, ESM-only. Runs on Node.js 23.6+, Bun 1.0+, and browsers. Dev console + production JSON from the same code.

Early release (0.x) — API may evolve before 1.0.

Quick Start ​

bash
npm install loggily
bash
bun add loggily
bash
pnpm add loggily
bash
yarn add loggily
typescript
import { createLogger } from "loggily"
import { toOtel } from "loggily/otel"
import { withMetrics, createMetricsCollector } from "loggily/metrics"
import * as otelApi from "@opentelemetry/api"

// One pipeline: console + OTEL + a Pino transport
const collector = createMetricsCollector()
const log = withMetrics(collector)(
  createLogger("myapp", [
    { level: "debug" },
    toOtel({ api: otelApi }),
    { write: (event) => pinoTransport.write(event), objectMode: true },
    console,
  ]),
)

// Structured logging — ?. skips everything when the level is disabled
log.info?.("server started", { port: 3000 })
log.debug?.("cache hit", { key: "user:42" })
log.error?.(new Error("connection lost"))

// Spans — automatic timing, parent-child tracking, trace IDs
{
  using span = log.span("db:query", { table: "users" })
  const users = await db.query("SELECT * FROM users")
  span.spanData.count = users.length
}
// → SPAN myapp:db:query (45ms) {count: 100, table: "users"}
// → also forwarded to OTLP backend and Pino transport

// Metrics — check p50/p95/p99 from explicit collector
for (const [name, s] of collector.all()) {
  if (s.p95 > 100) console.warn(`${name} is slow: p95=${s.p95}ms`)
}