Logging/Printing utility for vorpal.

Usage no npm install needed!

<script type="module">
  import vorpalLog from 'https://cdn.skypack.dev/vorpal-log';


Vorpal - Log

Build Status

A Vorpal.js extension adding simple logging methods.


npm install vorpal-log
npm install vorpal

Getting Started

const vorpal = (require('vorpal'))();
const vorpalLog = require('vorpal-log');

  .delimiter('vorpal-log demo 


const logger = vorpal.logger;

  .action(function(args, cb) {
  logger.debug('Log command called without arguments.');
  logger.log('Foo, bar, baz!');
  logger.confirm('You successfully ran the log command.');
  logger.info('It logs stuff.');
  logger.warn('Careful with that axe, Eugene!');
  logger.error('Something went wrong...');
  logger.fatal('If this was a real program, it would probably shut down now.');

logger.info('This is a demo program for the vorpal-log extension.');
logger.info('Run log to produce some output.');
logger.info('Run loglevel <level> to change the level, e.g. \'loglevel warn\'');

Default Functionality

Vorpal-log comes with the following predefined methods for logging:

  • logger.debug(msg) (loglevel 10)
  • logger.log(msg) (loglevel 20)
  • logger.info(msg) (loglevel 20)
  • logger.confirm(msg) (loglevel 20)
  • logger.warn(msg) (loglevel 30)
  • logger.error(msg) (loglevel 40)
  • logger.fatal(msg) (loglevel 50)

logger.printMsg(msg) will always print the message without caring about the loglevel or formatting.

Set the loglevel:


E.g. logger.setFilter('warn') will only print messages via logger.warn, logger.error and logger.fatal.


The following options passed by vorpal.use(vorpalLogger, options) are used:

  • printDate: If this is true, the default formatters begin each message with the current date.
  • preformat: a function which is passed the message and which returns a string which should be logged instead by the default formatters. Could for example be used to render marked.


Vorpal-log adds the following (hidden) command, which simply delegates to logger.setFilter. As a user can enable debug logging with it, you might want to remove it for production.

Usage: loglevel [options] <level>

set the log level


  --help  output usage information


logger.addFormatter(name, level, format)

Creates a logger[name] function, which will log the result of format(msg) with loglevel level. Use this to add custom formatters.

See customFormatter here for a working, insightful and useful example.


Takes either a custom filter function, a string, or a number.

When logging something, the formatter is passed to the function set by logger.setFilter. Logging only happens if this function returns true.

If logger.setFilter is passed a function, this function is the new filter function.

If passed a number, the new filter function will only log, if formatter.level is greater than or equal to that number.

If passed a string, the new filter function will only log if formatter.level is greater than or equal to formatters[filter].level.