@future-widget-lab/logger

An opinionated but minimal logger built on top of loglevel. It allows you to define custom log levels, emojis for different log types, and control debug level logs based on command-line arguments.

Features

Custom log levels and message formatting.
Debug logging controlled by command-line arguments.
Fine-grained control over debug visibility using tags.
Emoji support for different log types.
Optional side effects after a message is printed.

Installation

npm install @future-widget-lab/logger

Usage

Basic Example

import { createLogger } from '@future-widget-lab/logger';

const logger = createLogger({
  level: 'info'
});

logger.info({}, 'Application started');
logger.error({ errorCode: 500 }, 'Internal server error');

Debugging

To enable debug logs for a specific tag, add the corresponding command-line arguments to the command.

DEBUG="auth-mode" node example.mjs

const logger = createLogger({
  level: 'DEBUG',
  allTag: 'all',
  debugArgumentName: 'DEBUG'
});

logger.debug('auth-module', { user: 'test' }, 'Authentication successful');

You can also use the catch-all tag:

DEBUG="all" node example.mjs

Customizing Log Emojis

const logger = createLogger({
  level: 'info',
  debugEmoji: '🐛',
  errorEmoji: '❌',
  infoEmoji: 'ℹ️',
  traceEmoji: '🔍',
  warnEmoji: '⚠️'
});

Handling Log Side Effects

You can perform custom actions after a log message is printed by using the onAfterMessage option. The logger handles formatting, while onAfterMessage can trigger side effects such as API calls.

const logger = createLogger({
  level: 'info',
  onAfterMessage: ({ level, timestamp, payload, message }) => {
    sendLogToAnalytics({ level, timestamp, payload, message });
  }
});

API Reference

`createLogger(options: CreateLoggerOptions)`

Creates a new logger instance with the specified configuration options.

Options

Option	Type	Default	Description
`level`	`LogLevelDesc`		Sets the default log level.
`allTag`	`string`	`'all'`	Catch-all tag for debug logs.
`debugArgumentName`	`string`	`'DEBUG'`	Name of the command-line argument for debug logs.
`shouldDebug`	`ShouldDebug`	Internal Helper	Custom function to determine if debug logs should be printed.
`debugEmoji`	`string`	`'🕵'`	Emoji for debug logs.
`errorEmoji`	`string`	`'📕'`	Emoji for error logs.
`infoEmoji`	`string`	`'📘'`	Emoji for info logs.
`traceEmoji`	`string`	`'📓'`	Emoji for trace logs.
`warnEmoji`	`string`	`'📒'`	Emoji for warn logs.
`onMessage`	`function`	`undefined`	Custom message formatting handler.
`onAfterMessage`	`function`	`undefined`	Side-effect handler after logging.

Methods

debug(tag: string, object: object, message: string): Logs a debug message.
error(object: object, message: string): Logs an error message.
info(object: object, message: string): Logs an informational message.
trace(object: object, message: string): Logs a trace message.
warn(object: object, message?: string): Logs a warning message.

License

MIT