Lolog

me and the logs.

Introduction

Ease to logging your app with wrapping winston to own logger class which called Lolog

Supported level:

1. error
2. warn
3. info
4. debug

Available transports

1. ConsoleTransport
2. FileTransport

Usage

const { Format, Lolog, Transports } = require("@mqnoy/lolog");
const path = require("path");

const env = "dev";

class App {
  constructor() {
    const format =
      env === "local"
        ? Format.DefaultFormat()
        : Format.ElasticFormat({
            serviceName: "AppChild",
          });

    this.logger = new Lolog({
      level: "info",
      defaultMeta: { service: "APP" },
      format,
      transports: [
        Transports.FileTransport({
          filename: path.join(__dirname, "logs", "combined.log"),
        }),
        Transports.FileTransport({
          filename: path.join(__dirname, "logs", "error.log"),
          level: "error",
        }),
        Transports.ConsoleTransport(),
      ],
    });
  }

  dummyFunc = () => {
    const logger = this.logger.setChild({ "request.id": "abc123" });
    logger.info("test info");
    logger.warn("test warn");

    try {
      throw new Error("Database connection failed");
    } catch (error) {
      logger.debug("ada error di dummyFunc");
      logger.error(error);
      logger.error(error, { requestId: "abc123", userId: "u456" });
    } finally {
      this.dummyFunc2();
    }
  };
  
  dummyFunc2 = () => {
    this.logger.debug("dummyFunc2");
  };
}

const app = new App();
app.dummyFunc();

Output

Elastic format

{
    "@timestamp": "2025-05-04T11:59:46.972Z",
    "data": [
        1,
        2,
        3
    ],
    "ecs.version": "8.10.0",
    "error": {
        "message": "duarrr",
        "stack_trace": "Error\n    at HttpException (.../src/example/....."
        "type": "HttpException"
    },
    "event.dataset": "AppChild",
    "log.level": "error",
    "message": "duarrr",
    "request.id": "abc123",
    "service": "APP",
    "service.name": "AppChild",
    "userId": "u456"
}

Printf format

[2025-05-04T13:10:41.054Z] [ERROR]: duarrr
Error
    at HttpException (..../lolog/example/basic.ts:12:18)....
meta: {
  "request.id": "abc123",
  "data": [
    1,
    2,
    3
  ],
  "userId": "u456",
  "service": "APP"
}

TODO

• [ ] well documented
• [ ] unit test
• [ ] integrate with any log agent
• [ ]