Verba

Node logging library

Overview

Node logging library.

Usage Overview

Install

npm i -S verba

Basic Usage

import verba from 'verba'

const log = verba()

log.info('...')
log.step('...')
log.warn('...')
log.success('...')
log.json({ foo: 'bar' })
log.table([
  { foo: 1, bar: 2 },
  { foo: 3, bar: 4 },
])
log.spacer()
log.divider()
const spinner = log.spinner('...')
spinner.text('...')
const bar = log.progressBar({ /* ... */ })
bar.update(20) // 20%

Advanced Usage

Defining allowed log codes and log message data:

type LogCode = 'INIT' | 'ENV_VALIDATE' | 'CONNECT_DB' | ...
type LogData = { verbose: boolean, ... }
const log = verba<LogCode, LogData>()

Message formatting, log codes, and log data:

log.info({
  msg: f => `${f.green('Hello')}, ${f.blue('world!')}`,
  code: 'HELLO_WORLD_MSG',
  data: { verbose: true }
})

Providing default log codes and indentation:

const childTaskLog = log.child({ code: 'CHILD_TASK', indent: 2 })
childTaskLog.info('...')
childTaskLog.step('...')

Loading spinners (only for TTY consoles):

const spinner = log.spinner('Doing job')
// Update spinner text when progress updates occur
spinner.text('Doing job | 100%')
// Either clear the spinner and text line...
spinner.clear()
// ...Or stop the spinning and leave in console
spinner.persist()
log.success('Finished job')

Disabling colors for a Transport:

import verba, { consoleTransport } from 'verba'
const colorlessTransport = consoleTransport({
  disableColors: true
})
const log = verba({
  Transports: [colorlessTransport]
})

Using both console and file built-in Transports:

import verba, { consoleTransport, fileTransport } from 'verba'
const log = verba({
  Transports: [consoleTransport(), fileTransport()]
})

For more usage information, see the next sections.

Transports

Where and how Verba logs are outputted can be defined by Transports.

Verba has two built-in Transports: consoleTransport and fileTransport (defined at ./src/verba/transport). By default, consoleTransport is used.

Custom Transports can be a way to define completely different ways to output log messages. For example:

import verba, { VerbaTransport } from 'verba'

const transport: VerbaTransport = (
  // The original options received from the top-level `verba` instance.
  loggerOptions,
  // A listener store providing the ability to listen to various events of the verba instance.
  listeners
) => {
  /* ...Setup (ran once)... */
  // Called every time a verba logger instance is nested.
  return nestState => {
    /* ...Setup (ran for every nested logger)... */
    // Return an object that instructs how the Transport outputs log messages.
    return {
      log: msg => { /* ... */ },
      info: options => { /* ... */ },
      step: options => { /* ... */ },
      success: options => { /* ... */ },
      /* ...Rest of outlets... */
    }
  }
}

const log = verba({ transports: [transport] })

Aliases

Aliases can be used to:

1. Add new custom outlets.
2. Modify built-in outlets (i.e. log, info, step, etc.).
3. Exclude built-in outlets.

This can be useful when you need to:

1. Integrate Verba into a legacy codebase by allowing you to modify the arguments of built-in outlets.
2. Add new custom outlets that do conveninent/custom log output that would otherwise need multiple log calls (i.e. boxes, banners, etc.).
3. Exclude built-in outlets that you don't want for your application.

Note: Aliases that define new outlets will not interact with any defined Transports or Outlet Filters of the logger instance.

Example 1 - Adding a new header outlet

import verba from 'verba'

const log = verba().setAliases({
  header: logger => (s: string) => {
    logger.log(f => f.bold(f.italic(`-- ${s} --`)))
    logger.spacer()
  },
})

Example 2 - Modifying the built-in warn outlet

import verba from 'verba'

type MyLegacyCodebaseLogOptions = {
  message: string
  severity: 'urgent' | 'critical' /* | ... */
}

const log = verba().setAliases({
  // Provide a shim for the built-in `warn` outlet
  warn: logger => (options: MyLegacyCodebaseLogOptions) => {
    logger.warn({
      msg: options.message,
      data: { severity: options.severity },
    })
  },
})

Example 3 - Excluding the built-in info outlet

import verba from 'verba'

const log = verba().setAliases({
  warn: false
})

Outlet Filters

Verba log messages can be included and excluded via Outlet Filters.

Outlet Filters filter messages before Transports.

One can filter based on any aspect of any log message, for example the Outlet of the log message (e.g. log, step, info, table, json, etc.), the options supplied to them, the data supplied to table, and so on.

Example 1 - Exclude tables over 5 rows

import verba, { OutletFilter } from 'verba'

const excludeLargeTables: OutletFilter = options => (
  options.outlet !== Outlet.TABLE || options.data?.length < 6
)
const log = verba({
  outletFilters: [excludeLargeTables]
})
log.table([1, 2, 3, 4, 5]) // Included
log.table([1, 2, 3, 4, 5, 6]) // Excluded

Example 2 - Exclude verbose logs

import verba, { OutletFilter } from 'verba'

type LogMessageData = { verbose: boolean }
const excludeVerbose: OutletFilter<string, LogMessageData> = options => (
  !options.options.data.verbose
)
const log = verba<string, LogMessageData>({
  outletFilters: [excludeVerbose]
})
log.info({
  msg: 'This is verbose and therefore excluded',
  data: { verbose: true }
})

Examples

An example app that fully demonstrates the usage of Verba is at ./examples/app-base.

To see how to run the examples locally, see ./contributing/development.md#examples.

Development

Install NPM dependencies:

npm i

Task	Command
Lint	npm run lint
Test	npm run test
Build	npm run build
Run example app	npm run example

See ./contributing/development.md for more information.

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