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 400 bytes with 0 dependencies
• JSON configuration
• 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
  • Dynamically combine any of the above or try something new
• 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

Example

log.error('security', 'not authorized', statusCode);
log.warn('transporter', 'Evil twin detected!');

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. When a message's level is greater than or equal to its tag's assigned level, missionlog executes a callkack. This simple and elegant approach to logging is incredibly flexible. For example, with missionlog you can seamlessly migrate from console logging to a sophisticated cloud service with minimal impact!

// var log = require('missionlog').log;
improt { log } from 'missionlog';

/**
 * init
 * @param config JSON object which assigns tags levels. If uninitialized,
 *    a tag's level defaults to INFO where ERROR > WARN > INFO.
 * @param callback? supports logging whatever way works best for you
 * @return {Log} supports chaining
 */
log.init(
  { loader: 'INFO', security: 'ERROR', system: 'OFF' },
  (level, tag, msg, params) => {
    const prefix = `${level}: [${tag}] `;
    switch(level) {
      case 'ERROR':
        console.error(prefix, msg, ...params);
        break;
      case 'WARN':
        console.warn(prefix, msg, ...params);
        break;
      case 'INFO':
        console.info(prefix, msg, ...params);
        break;
    }
  });

Usage

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

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

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