@jenesei-software/jenesei-library-log

A lightweight logging library for Node.js and browser projects written in TypeScript or JavaScript.

Features:

• built-in log types;
• colored console output based on log type;
• stdout and stderr routing per message type;
• browser-friendly console output;
• custom log types;
• separate logger instances for different services or modules.

Installation

npm i @jenesei-software/jenesei-library-log

Quick Start

import { logger } from '@jenesei-software/jenesei-library-log';

logger.info('Server started');
logger.success('Database connected');
logger.warn('Cache is disabled');
logger.error('Unexpected error', { code: 'E_DB' });
logger.debug('Payload', { page: 1, limit: 20 });

Example output:

[2026-04-18T03:10:52.109Z] [INFO] Server started
[2026-04-18T03:10:52.111Z] [SUCCESS] Database connected
[2026-04-18T03:10:52.112Z] [WARN] Cache is disabled

Default Types

The library ships with these log types:

• info
• success
• warn
• error
• debug

Each type can be configured with:

• label - console label text;
• color - output color;
• stream - stdout or stderr;
• enabled - whether the type is enabled;
• timestamp - whether this type includes a timestamp.

Creating a Custom Logger

import { createLogger } from '@jenesei-software/jenesei-library-log';

const appLogger = createLogger({
  name: 'api',
  timestamp: true,
});

appLogger.info('HTTP server is ready');
appLogger.error('Cannot connect to Redis');

Output will look like this:

[2026-04-18T03:12:41.000Z] [api] [INFO] HTTP server is ready

Overriding Default Types

import { createLogger } from '@jenesei-software/jenesei-library-log';

const logger = createLogger({
  types: {
    info: {
      label: 'LOG',
      color: 'cyan',
    },
    debug: {
      enabled: false,
    },
  },
});

logger.info('Custom info message');
logger.debug('This line will not be printed');

Adding Custom Types

You can add your own types when creating the logger:

import { createLogger } from '@jenesei-software/jenesei-library-log';

const logger = createLogger({
  types: {
    http: {
      label: 'HTTP',
      color: 'magenta',
    },
    audit: {
      label: 'AUDIT',
      color: 'white',
    },
  },
});

logger.log('http', 'GET /users', 200);
logger.log('audit', 'User deleted', { id: 42 });

Or register a new type later:

import { createLogger } from '@jenesei-software/jenesei-library-log';

const logger = createLogger();

logger.registerType('queue', {
  label: 'QUEUE',
  color: 'brightMagenta',
});

logger.queue('Job started', { id: 'job-1' });
logger.log('queue', 'Job finished');

Available Colors

Supported values:

• black
• red
• green
• yellow
• blue
• magenta
• cyan
• white
• gray
• brightRed
• brightGreen
• brightYellow
• brightBlue
• brightMagenta
• brightCyan
• brightWhite

You can also pass your own color function:

import { createLogger } from '@jenesei-software/jenesei-library-log';

const logger = createLogger({
  types: {
    metric: {
      label: 'METRIC',
      color: (message) => `\u001B[36m${message}\u001B[0m`,
    },
  },
});

logger.log('metric', 'Requests per second', 128);

Runtime Control

import { createLogger } from '@jenesei-software/jenesei-library-log';

const logger = createLogger();

logger.setTypeEnabled('debug', false);
logger.setColorsEnabled(false);

Useful methods:

• logger.log(type, ...messages) - log a message by type name;
• logger.registerType(type, config) - add a new type;
• logger.hasType(type) - check whether a type is registered;
• logger.getTypes() - get the current type map;
• logger.setTypeEnabled(type, enabled) - enable or disable a type;
• logger.setColorsEnabled(enabled) - enable or disable colors.

Using It in Node.js

Example for a simple Node.js service:

import { createServer } from 'node:http';
import { createLogger } from '@jenesei-software/jenesei-library-log';

const logger = createLogger({
  name: 'node-app',
  types: {
    http: {
      label: 'HTTP',
      color: 'brightCyan',
    },
  },
});

const server = createServer((request, response) => {
  logger.log('http', request.method, request.url);
  response.end('ok');
});

server.listen(3000, () => {
  logger.success('Server started on port 3000');
});

Using It in the Browser

import { createLogger } from '@jenesei-software/jenesei-library-log';

const logger = createLogger({
  name: 'web-app',
  types: {
    ui: {
      label: 'UI',
      color: 'brightMagenta',
    },
  },
});

logger.info('Application booted');
logger.log('ui', 'Sidebar opened');
logger.error('Unexpected client error', new Error('Network timeout'));

In the browser, the logger uses console.log and console.error, and built-in colors are rendered with %c styles.

Notes

• In Node.js, colors are automatically disabled when the console does not support TTY.
• If the NO_COLOR environment variable is set, colored output is disabled.
• error and warn use stderr by default.
• In the browser, stdout maps to console.log and stderr maps to console.error.