missionlog

Lightweight logger with an extensible configuration. Supports level based filtering and tagging. Filtering keeps your logs readable and uncluttered while tagging makes them searchable.

Features

• Small footprint, around 500 bytes with 0 dependencies
• Filter by level, ERROR > WARN > INFO
• Filter by tag, 'security' | 'whatever'
• Log callback is extensible from console to cloud
  • Style terminal output with chalk
  • Send JSON to a cloud service like Loggly
  • Log strings and objects to the console
  • Combine any of the above based on env
• API mirrors console.log, logs objects and supports rest parameters
• Works reliably with node or any browser through a bundler
• 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.

// var log = require('missionlog').log;
import { log, LogLevel } from 'missionlog';

/**
 * initialize missionlog
 * @param config JSON which assigns tags levels. An uninitialized,
 *    tag's level defaults to INFO.
 * @param callback? handle logging whichever way works best for you
 */
log.init(
  { transporter: 'INFO', security: 'ERROR', system: 'OFF' },
  (level, tag, msg, params) => {
    const prefix = `${level}: [${tag}] `;
    switch(level) {
      case LogLevel.ERROR:
        console.error(prefix, msg, ...params);
        break;
      case LogLevel.WARN:
        console.warn(prefix, msg, ...params);
        break;
      case LogLevel.INFO:
        console.info(prefix, msg, ...params);
        break;
    }
  });

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');

// 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');