missionlog

Lightweight logger with an easy configuration. Supports level based filtering and tagging that keeps your logs readable and uncluttered!

Features

• Small footprint, around 500 bytes
• Filter by level, ERROR > WARN > INFO > TRACE > DEBUG
• Filter by tag, 'security' | 'anything'
• Log callback is extensible from console to cloud
  • Style terminal output with chalk and log to the console
  • Send JSON to a cloud service like Loggly
• API mirrors console, logs objects and supports rest parameters
• Works reliably with node or any browser
• Includes TypeScript definitions so no need for external @types

Install

npm install missionlog

Initialize

Tags typically refer to a subsystem or component like 'security' or FooBar.name. When missionlog is initialized, tags can be assigned a level. A message is logged when its level is greater than or equal to its tag's assigned level.

import { log, LogLevel } from 'missionlog';
import chalk from 'chalk';

// handler which does the logging to the console or anything
const logger = {
  [LogLevel.ERROR]: (tag, msg, params) => console.error(`[${chalk.red(tag)}]`, msg, ...params),
  [LogLevel.WARN]: (tag, msg, params) => console.warn(`[${chalk.yellow(tag)}]`, msg, ...params),
  [LogLevel.INFO]: (tag, msg, params) => console.log(`[${chalk.brightGreen(tag)}]`, msg, ...params),
  [LogLevel.TRACE]: (tag, msg, params) => console.log(`[${chalk.cyan(tag)}]`, msg, ...params),
  [LogLevel.DEBUG]: (tag, msg, params) => console.log(`[${chalk.magenta(tag)}]`, msg, ...params),
} as Record<LogLevel, (tag: string, msg: unknown, params: unknown[]) => void>;

/**
 * initialize missionlog
 * @param config JSON which assigns tags levels. An uninitialized,
 *    tag's level defaults to DEBUG.
 * @param callback? handle logging whichever way works best for you
 */
log.init({ transporter: 'INFO', security: 'ERROR', system: 'OFF' }, (level, tag, msg, params) => {
  logger[level as keyof typeof logger](tag, msg, params);
});

Usage

import { log, tag } from 'missionlog';

// the imported value "tag" is populated with YOUR tags!
log.error(tag.security, 'not authorized', statusCode);

// but if you prefer simply use strings
log.warn('transporter', 'Evil twin detected!');

// filtered since security's log level ERROR is greater than INFO
log.info(tag.security, 'login successful');

// trace
log.trace(tag.system, 'entering engine room');

// debug
log.debug(tag.system, { warpFactor, starDate });

// also filtered since system's level is OFF
log.error(tag.system, 'eject the warp core', error);

// updates tag levels on the fly
log.init({ loader: 'ERROR', system: 'INFO' });

// disable logging by clearing the callback
log.init();

Advanced Usage

Create an instance with its own tags and callback.

import { Log, tag } from 'missionlog';

const myLog = new Log().init(
  { loader: 'INFO', security: 'ERROR' },
  (level, tag, msg, params) => {
    console.log(`${level}: [${tag}] `, msg, ...params);
});

myLog.info(tag.security, 'login successful');