Minimalist Logger

A minimalist logger for Node.js. Log output format is something like Java Log4j format.

This is a stdout / stderr only logger. If you need more of this, then check out other loggers.

Supports both ESM and CommonJS module systems.

Environment variables

- LOG_LEVEL - Log level. Default: DEBUG. Possible values: DEBUG, INFO, WARN, ERROR.
- ROOT_LOGGER_NAME - Root logger name. Default: app.

Usage

``ts
import logger from '@janez89/logger';

logger.info('Hello world from App Logger!');
`

__Output__:

`
2025-12-17 13:19:19.546 INFO 74822 --- app: Logger initialized. Global log level: DEBUG. Node version: v22.15.0
2025-12-17 13:19:19.546 DEBUG 74822 --- app: Use LOG_LEVEL=INFO to decrease verbosity. Supported values: DEBUG, INFO, WARN, ERROR
2025-12-17 13:19:19.546 INFO 74822 --- app: Hello world from App Logger!
`

`ts
import { getLogger } from '@janez89/logger';

const logger = getLogger('namespaced-logger');

logger.debug('Doing something...', { foo: 'bar' });
logger.info('Hello world from namespaced Logger!');
logger.warn('Something is not right...');
logger.error('Something went wrong!', new Error('Oops!'));
logger.log('INFO', 'Parameterized log level');
`

__Output__:

`
2025-12-17 15:17:39.775 INFO 79680 --- app: Logger initialized. Global log level: DEBUG. Node version: v22.15.0
2025-12-17 15:17:39.776 DEBUG 79680 --- app: Use LOG_LEVEL=INFO to decrease verbosity. Supported values: DEBUG, INFO, WARN, ERROR
2025-12-17 15:17:39.776 DEBUG 79680 --- namespaced-logger: Doing something... {"foo":"bar"}
2025-12-17 15:17:39.776 INFO 79680 --- namespaced-logger: Hello world from namespaced Logger!
2025-12-17 15:17:39.776 WARN 79680 --- namespaced-logger: Something is not right...
2025-12-17 15:17:39.776 ERROR 79680 --- namespaced-logger: Something went wrong! Error: Oops!
at (.../logger/src/hello.ts:10:39)
at ModuleJob.run (node:internal/modules/esm/module_job:274:25)
at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:644:26)
at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:116:5)
2025-12-17 15:17:39.776 INFO 79680 --- namespaced-logger: Parameterized log level
`

!Screenshot

API

`ts
type LogLevel = 'DEBUG' | 'INFO' | 'WARN' | 'ERROR';

interface Logger {
debug: (...args: unknown[]) => void;
info: (...args: unknown[]) => void;
warn: (...args: unknown[]) => void;
error: (...args: unknown[]) => void;
log: (level: LogLevel, ...args: unknown[]) => void;
level: LogLevel;
name: string;
}

declare const logger: Logger;

/**
* Get a logger instance with the specified name.
* @param name Name of the logger.
* @param logLevel Log level for the logger. Defaults to the global log level.
*/
export declare function getLogger(name: string, logLevel?: LogLevel): Logger;
export default logger;
``

History

- 1.0.0 Initial release