@rx-ted/logger

A lightweight logging library with modular architecture — Logger, Handler, and Formatter separation. Supports multiple handlers, child loggers, and file rotation.

Features

• Modular Architecture: Logger → Handler → Formatter separation
• Multiple Handlers: Console and File handlers with independent configuration
• Child Loggers: Inheritance with scope-based namespaces
• File Rotation: Auto-dated filenames with max file count limits
• Dual Formatters: JSON and TEXT formats
• Multi-Runtime: Works with Bun, Node.js, Deno, and Cloudflare Workers

Install

pnpm add @rx-ted/logger

Quick Start

import { Logger } from "@rx-ted/logger";

const logger = new Logger({ name: "app" });

logger.info("Hello World");
logger.debug("Debug info", { userId: 123 });
logger.warn("Warning message");
logger.error("Error occurred", { code: "ERR_001" });

Logger Options

| Option | Type | Default | Description | | ----------- | ---------------------------------------- | --------- | ---------------------- | | name | string | 'app' | Logger namespace | | scope | string | - | Child logger scope | | level | 'debug' \| 'info' \| 'warn' \| 'error' | 'info' | Log level | | handlers | HandlerConfig[] | console | Handler configurations | | propagate | boolean | true | Propagate to parent | | onError | (err: LogError) => void | - | Error callback |

Handlers

Console Handler

const logger = new Logger({
  name: "app",
  handlers: [
    {
      type: "console",
      level: "debug",
      formatter: {
        type: "text",
        template: "[{time}] [{level}] {namespace}: {message}",
        colors: true,
      },
    },
  ],
});

File Handler

const logger = new Logger({
  name: "app",
  handlers: [
    {
      type: "file",
      level: "info",
      formatter: { type: "json" }, // or 'text'
      maxSize: "10MB", // default: 10MB
      maxFiles: 7, // default: 7
    },
  ],
});

File handler features:

• Auto-dated filenames: app.2026-04-20.json
• Automatic old file cleanup when exceeding maxFiles
• Automatic date rollover at midnight

Child Loggers

const logger = new Logger({ name: "app" });

const child = logger.child("module");

console.log(child.namespace); // "app.module"

Child loggers:

• Inherit parent's handlers by default
• Inherit parent's level
• Disable propagation by default (set propagate: true to enable)
• Require scope option (cannot use name)

Methods

• debug(message, context?) - Debug level
• info(message, context?) - Info level
• warn(message, context?) - Warning level
• error(message, context?) - Error level
• child(scope, options?) - Create child logger
• setLevel(level) - Change log level
• addHandler(handler) - Add handler
• close() - Close all handlers

Error Handling

const logger = new Logger({
  name: "app",
  handlers: [
    {
      type: "file",
      onError: (err) => {
        console.error("Handler error:", err.error);
      },
    },
  ],
  onError: (err) => {
    console.error("Logger error:", err.error);
  },
});

Runtime Notes

• File handler is automatically disabled in Cloudflare Workers environment
• Supports Bun, Node.js, and Deno runtimes

Testing

pnpm test          # Run tests
pnpm test:coverage     # Run with coverage