log-formatter

Simple formatting for logging

npm install @mojule/log-formatter

usage

default logger

import { logger } from '@mojule/log-formatter'

or:

const { logger } = require( '@mojule/log-formatter' )

logger.time( 'My program' )

logger.trace( 'My program trace' )
logger.debug( 'Debug', { foo: { bar: { baz: [ 1, 2, 3 ] } } } )
logger.info( 'Hello, world!', 1, [ 1, 2, 3 ], 'etc' )

try {
  logger.warn( 'Uh oh' )

  throw Error( 'A bad thing happened' )
} catch( err ){
  logger.error( err )
} finally {
  logger.fatal( 'Exiting program because of the bad thing' )
  logger.time( 'My program' )
}

• logger.trace, logger.debug, logger.time go to console.debug
• logger.info goes to console.info
• logger.warn goes to console.warn
• logger.error and logger.fatal goes to console.error

Note that trace and time are handled internally for consistency of formatting rather than using console.trace or console.time

time    2019-08-08T00:40:02.752Z        Start   My program
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
trace   2019-08-08T00:40:02.758Z        My program trace
────────────────────────────────────────────────────────────────────────────────
Trace:
    at Object.<anonymous> (log-formatter/examples/default.js:5:8)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:742:12)
    at startup (internal/bootstrap/node.js:279:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:752:3)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
debug   2019-08-08T00:40:02.759Z        Debug
────────────────────────────────────────────────────────────────────────────────
{
  "foo": {
    "bar": {
      "baz": [
        1,
        2,
        3
      ]
    }
  }
}
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
info    2019-08-08T00:40:02.760Z        Hello, world!   1       [ 1, 2, 3 ]     etc
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
warn    2019-08-08T00:40:02.760Z        Uh oh
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
error   2019-08-08T00:40:02.760Z        Error   A bad thing happened
────────────────────────────────────────────────────────────────────────────────
Error: A bad thing happened
    at Object.<anonymous> (log-formatter/examples/default.js:12:9)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:742:12)
    at startup (internal/bootstrap/node.js:279:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:752:3)
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
fatal   2019-08-08T00:40:02.761Z        Exiting program because of the bad thing
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
time    2019-08-08T00:40:02.761Z        End     My program      0s 9.330659ms
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

simple file logger

createLogger allows you to provide functions to call for each of the logging levels rather than using the defaults, which go to stdout and stderr

The functions you provide are called with a single string argument containing the message

All functions are optional, if you don't provide them, the output will go nowhere - you can use this to implement custom logging levels

import { createLogger } from '@mojule/log-formatter'
import { appendFile } from 'fs'

or:

const { createLogger } = require( '@mojule/log-formatter' )
const { appendFile } = require( 'fs' )

const stdOut = './examples/stdout.txt'
const stdErr = './examples/stderr.txt'

const append = ( path, data ) => appendFile(
  path, data + '\n', 'utf8', err => {
    if( err ) console.error( err )
  }
)

const writeOut = content => append( stdOut, content )
const writeErr = content => append( stdErr, content )

const trace = writeOut
const debug = writeOut
const time = writeOut
const info = writeOut
const warn = writeErr
const error = writeErr
const fatal = writeErr

const options = {
  trace, debug, time, info, warn, error, fatal
}

const logger = createLogger( options )

logger.time( 'My program' )

logger.trace( 'My program trace' )
logger.debug( 'Debug', { foo: { bar: { baz: [ 1, 2, 3 ] } } } )
logger.info( 'Hello, world!', 1, [ 1, 2, 3 ], 'etc' )

try {
  logger.warn( 'Uh oh' )

  throw Error( 'A bad thing happened' )
} catch( err ){
  logger.error( err )
} finally {
  logger.fatal( 'Exiting program because of the bad thing' )
  logger.time( 'My program' )
}