node-logutil

Simple log formatting for Node 6.x and 8.x

Installation

npm install https://github.com/connectedcars/node-logutil#v1.1.0

API

log.debug(message[, context])

Logs the provided message with the optional context as a JSON string, if the log level is set to output debug.

The method takes most input, but the combination described above is the recommended one.

message

Type: string

Descriptive log message

context

Type: object

Object hash to provide log context.

log.statistic(message[, context])

Logs the provided message with the optional context as a JSON string, if the log level is set to output statistic.

The method takes most input, but the combination described above is the recommended one.

message

Type: string

Descriptive log message

context

Type: object

Object hash to provide log context.

log.info(message[, context])

Logs the provided message with the optional context as a JSON string, if the log level is set to output info.

The method takes most input, but the combination described above is the recommended one.

message

Type: string

Descriptive log message

context

Type: object

Object hash to provide log context.

log.warn(message[, context])

Logs the provided message with the optional context as a JSON string, if the log level is set to output warnings.

The method takes most input, but the combination described above is the recommended one.

message

Type: string

Descriptive log message

context

Type: object

Object hash to provide log context.

log.error(message[, context])

Logs the provided message with the optional context as a JSON string, if the log level is set to output errors.

The method takes most input, but the combination described above is the recommended one.

message

Type: string

Descriptive log message

context

Type: object

Object hash to provide log context.

Usage

const log = require('logutil')

log.debug('This is a debug message')
// Outputs to stdout: {"message":"This is a debug message","level":"DEBUG","timestamp":"2017-09-01T13:37:42Z"}
log.debug('This is a statistic value', { foo: 42, bar: 1337 })
// Outputs to stdout: {"message":"Statistics","level":"STATISTIC","timestamp":"2017-09-01T13:37:42Z", "content":{"foo":42,"bar":1337}}
log.info('This is an info message')
// Outputs to stdout: {"message":"This is an info message","level":"INFO","timestamp":"2017-09-01T13:37:42Z"}
log.warn('This is a warning message', { type: 'missing-item' })
// Outputs to stderr: {"message":"This is a warning message","level":"WARNING","timestamp":"2017-09-01T13:37:42Z","context":{"type":"missing-item"}}
log.error('This is an error message', { context: { items: ['foo', 'bar'] } })
// Outputs to stderr: {"message":"This is an error message","level":"ERROR","timestamp":"2017-09-01T13:37:42Z","context":{"items":["foo","bar"]}}

log.debug(() => {
  // Only runs if log level is debug
  return Promise.resolve('This is a debug message')
})
// Outputs to stdout: {"message":"This is a debug message","level":"DEBUBG","timestamp":"2017-09-01T13:37:42Z"}
log.info(() => {
  // Only runs if log level is info
  return new Promise(resolve => {
    setTimeout(() => {
      resolve('This is an info message')
    }, 500)
  })
})
// Outputs to stdout (after 500 ms): {"message":"This is an info message","level":"INFO","timestamp":"2017-09-01T13:37:42Z"}

Configuration

Determining what to output depends on the environment variable LOG_LEVEL. This variable can be DEBUG, INFO, WARN, or ERROR, but defaults to WARN.