dlog2

Isomorphic logging library for browser, Node, Bun and Deno.

Install

npm install dlog2

Quick start

import { initLogger, createLogger } from "dlog2";

// Global singleton logger
const logger = initLogger({ level: "debug" });
logger.info("app started");

// Contextual child logger with module/state tracking
const mod = createLogger("AuthModule");
mod.warn("token expired");

const http = createLogger("HTTP", ModuleState.RUNNING);
http.error("connection refused", { url: "/api/data" });

API

initLogger(options?)

Creates or returns the global singleton logger.

• level — log level (default: "info", env: LOG_LEVEL)
• transports — custom transport array (default: ConsoleTransport in dev, + FileTransport on Node)
• registerHandlers — attach process signal handlers (SIGINT/SIGTERM, unhandledRejection, uncaughtException)
• logDir — custom log directory (default: "./logs", env: LOG_DIR)

Returns a Logger instance.

createLogger(module?, state?)

Creates or returns a cached child logger from the global logger. Cached by "module:state" key.

const a = createLogger("Worker", ModuleState.RUNNING);
const b = createLogger("Worker", ModuleState.RUNNING);
a === b // true (cached)

logger.child(meta)

Creates a child logger inheriting level and transports, with merged meta.

const child = logger.child({ module: "SubMod", state: ModuleState.INITIALIZING });

logger.playerError(error, url?)

Logs an error with player error context. Accepts Error object or string + optional URL.

logger.playerError(new Error("timeout"));
logger.playerError("parse failed", "https://example.com/stream");

Level methods

logger.error("msg", meta?);
logger.warn("msg", meta?);
logger.info("msg", meta?);
logger.debug("msg", meta?);

logger.addTransport(transport)

Dynamically add a transport at runtime.

logger.end()

Finalises all transports (closes streams, etc.).

Transports

ConsoleTransport

Outputs formatted logs to console.error/warn/info/debug with ANSI colors.

import { ConsoleTransport } from "dlog2/transports/console";

FileTransport

Writes logs to a file with daily rotation (%DATE% placeholder in filename) and optional level filter.

import { FileTransport } from "dlog2/transports/file";

new FileTransport({
  filename: "app-%DATE%.log",
  level: "error",          // optional level filter
  logDir: "./custom-logs", // optional custom directory
});

Custom transport

import type { LogEntry, Transport } from "dlog2";
import { formatLog } from "dlog2/logger/formatters";

class MyTransport implements Transport {
  log(entry: LogEntry): void {
    const line = formatLog(entry, false);
    // send line somewhere
  }
}

initLogger({ transports: [new MyTransport()] });

Configuration

| Env | Default | Description | |-----|---------|-------------| | LOG_LEVEL | info | Default log level | | LOG_DIR | ./logs | Log directory for FileTransport | | LOG_LANG | — | dayjs locale | | DEBUG_ALL | — | Enable debug for all modules | | DEBUG_MODULES | — | Comma-separated module names with debug enabled | | DEBUG_EXCLUDE | — | Comma-separated module names excluded from debug | | SHOW_SOURCE | true | Show caller file:line in warn/error entries |