🪵 @yuva-devlab/logger

Lightweight, zero-dependency, isomorphic TypeScript logger and Express HTTP request logging middleware for the Yuva DevLab ecosystem.

Features

• 🎨 Colored Console Output: Distinct terminal colors for DEBUG, INFO, WARN, and ERROR levels with ISO-8601 timestamps.
• 🏷️ Context Support: Tag logs with component or service contexts (e.g., [AuthService], [HTTP]).
• 📁 File Persistence: Optional disk persistence using asynchronous Node.js file streams (LOG_PERSIST=true).
• 🌐 HTTP Request Middleware: Ready-to-use Express middleware tracking request methods, URLs, status codes, and execution durations.
• ⚙️ Environment Aware: Configurable through standard environment variables or explicit config options.
• 📦 Dual ESM & CJS Build: Works seamlessly across both modern ESM runtimes and legacy CommonJS environments.

Installation

pnpm add @yuva-devlab/logger
# or
npm install @yuva-devlab/logger

Quick Start

Basic Logger

import { Logger } from "@yuva-devlab/logger";

const logger = new Logger("AuthService");

logger.info("User logged in successfully", { userId: "user_123" });
logger.warn("Rate limit threshold approached", { ip: "192.168.1.1" });
logger.error("Failed to authenticate user", new Error("Token expired"));
logger.debug("Decoded JWT payload", { sub: "user_123" });

Configured Logger (with Environment Variables)

import { createLogger } from "@yuva-devlab/logger";

const logger = createLogger({
  level: "info",
  enabled: true,
  file: "./logs/app.log",
});

logger.info("Application initialized");

Express Request Logger Middleware

import express from "express";
import { requestLogger, Logger } from "@yuva-devlab/logger";

const app = express();
const httpLogger = new Logger("HTTP");

// Attach the middleware
app.use(requestLogger(httpLogger));

app.get("/api/users", (req, res) => {
  res.json([{ id: 1, name: "Alice" }]);
});

app.listen(3000, () => {
  httpLogger.info("Server started on port 3000");
});

Environment Variables

| Variable | Type | Default | Description | | :------------ | :-------- | :---------- | :------------------------------------------------------------------ | | LOG_ENABLED | boolean | true | Enable or disable all log output ("false" to mute). | | LOG_LEVEL | string | "info" | Minimum log level ("debug", "info", "warn", "error"). | | LOG_PERSIST | boolean | false | When "true", appends log output to disk file. | | LOG_FILE | string | undefined | File path to write log entries to (required if LOG_PERSIST=true). |

API Reference

Logger

• constructor(context?: string)
• log(message: any, ...optionalParams: any[]): void
• info(message: any, ...optionalParams: any[]): void
• warn(message: any, ...optionalParams: any[]): void
• error(message: any, ...optionalParams: any[]): void
• debug(message: any, ...optionalParams: any[]): void (suppressed automatically in NODE_ENV === "production")

createLogger(config?: LoggerConfig): Logger

Creates a configured logger honoring runtime configuration and environment variables.

loggerWithConfig(base: Logger, config?: LoggerConfig): Logger

Wraps an existing logger instance to respect runtime level gating and file persistence.

requestLogger(loggerInstance?: Logger): ExpressMiddleware

Express middleware logging incoming HTTP requests upon completion with status code-based log levels.

License

MIT © Yuva DevLab