Package Exports

missionlog

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Readme

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';

// after calling init the imported value "tag" is populated with the your tag values
log.error(tag.security, 'not authorized', statusCode);

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

// gets 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' });

// or disable all logging
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');