pretty-logger-js

pretty-logger-js

A lightweight, logging module that provides a plug-in style transmission and formatter.

Features

• Log levels: debug → info → warn → error → silent
• Formatters: plain text, colorized (dev), and JSON (production)
• Transports: Console, File (with rotation), HTTP
• Child loggers: inherit config, add scoped metadata
• Runtime control: change level or add/remove transports on the fly
• No external dependencies

Quick start

const { logger } = require('./pretty-logger-js');

logger.info('Server started', { port: 3000 });
logger.warn('High memory', { mb: 512 });
logger.error('DB failed', { host: 'localhost' });

Set the minimum level via the LOG_LEVEL environment variable (default: info):

LOG_LEVEL=debug node app.js

Custom logger

const {
  Logger,
  createConsoleTransport,
  createFileTransport,
  colorFormatter,
  jsonFormatter,
} = require('./pretty-logger-js');

const logger = new Logger({
  level: 'debug',
  name:  'my-app',          // added to every log entry's meta
  transports: [
    createConsoleTransport({ formatter: colorFormatter }),
    createFileTransport({
      filePath:  './logs/app.log',
      formatter: jsonFormatter,
      maxBytes:  10 * 1024 * 1024,  // 10 MB → then rotate
      maxFiles:  5,                  // keep 5 rotated files
    }),
  ],
});

Child loggers

Inherit all settings but inject extra metadata into every entry:

// In your request middleware:
const reqLogger = logger.child({ requestId: req.id, userId: req.user.id });
reqLogger.info('Request received', { method: req.method, path: req.path });
// → meta always contains requestId and userId

HTTP transport

Send logs to an external endpoint (e.g. a log aggregator):

const { createHttpTransport } = require('./pretty-logger-js');

const logger = new Logger({
  transports: [
    createHttpTransport({
      url:     'https://logs.example.com/ingest',
      headers: { Authorization: 'Bearer MY_TOKEN' },
      levels:  ['error', 'warn'],   // only send errors and warnings
      timeout: 3000,
    }),
  ],
});

Runtime control

// Silence all logs (e.g. in tests)
logger.setLevel('silent');

// Re-enable
logger.setLevel('info');

// Add a transport after creation
logger.addTransport(createFileTransport({ filePath: './debug.log' }));

// Remove a transport by name
logger.removeTransport('file');

Formatters

Formatter	Output	Best for
colorFormatter	[timestamp] [INFO ] message {"key":"value"} (ANSI colors)	Dev console
plainFormatter	[timestamp] [INFO ] message {"key":"value"} (no color)	File output
jsonFormatter	{"timestamp":"...","level":"info","message":"...","meta":{...}}	Production / log aggregators

Custom formatter

A formatter is just a function — write your own:

function myFormatter(level, message, meta) {
  return `${level.toUpperCase()} | ${message} | ${JSON.stringify(meta)}`;
}

createConsoleTransport({ formatter: myFormatter });

API reference

new Logger(options)

Option	Type	Default	Description
level	string	'info'	Minimum level to emit
transports	array	[]	Transport objects
defaultMeta	object	{}	Merged into every log entry's meta
name	string	—	Added as meta.logger

logger.log(level, message, meta?)

logger.debug/info/warn/error(message, meta?)

logger.child(meta) → Logger

logger.setLevel(level)

logger.addTransport(transport)

logger.removeTransport(name)

File structure

pretty-logger-js/
  index.js              ← public API + default instance
  logger.js             ← Logger class
  formatter.js          ← plain, color, JSON formatters
  transports/
    console.js          ← stdout/stderr transport
    file.js             ← file transport with rotation
    http.js             ← HTTP/HTTPS POST transport
  examples/
    basic.js            ← simple usage
    advanced.js         ← full feature demo
  README.md
  package.json

Running the examples

node examples/basic.js
node examples/advanced.js

Logs written to files will appear in ./logs/.

License

MIT