ConCol

A simple but flexible Node.js formatted color logger with no dependencies.

By default, time is shown in 24-hour HH:MM:SS.mmm and numbers are shown in #,### format.

Installation

npm install ConCol

Usage

import { ConCol } from 'ConCol';

// create logger instances
const log1 = new ConCol('App One', 'cyan');
const log2 = new ConCol('App Two', 'green');
const log3 = new ConCol('App Three 0123456789', 'white', 3);

// basic logging
log1.log('output single string');
log1.info('output string\nwith carriage returns');
log1.warn('show warning');
log1.error('show error');

/* output
12:30:07.030 App One       ┃ output a single string
10:54:34.645 App One       ┃ output string
10:54:34.645 App One       ┃ with carriage returns
10:54:34.646 App One       ┃  WARN: show warning
10:54:34.646 App One       ┃ ERROR: show error
*/

// name/value/unit
log2.log(['ConCol requires', 0, ' modules']);
log2.log([ 'fibonacci sequence', ['first', 1], ['second', 1], ['third', 2] ]);

/* output
10:54:34.697 App Two       ┃                ConCol requires:        0 modules
10:54:34.697 App Two       ┃ output the fibonacci sequence
10:54:34.697 App Two       ┃                          first:        1
10:54:34.697 App Two       ┃                         second:        1
10:54:34.697 App Two       ┃                          third:        2
*/

// log level filtering
log3.info('level0', 0);
log3.info('level3', 3);
log3.info('level4', 4); // not shown - log level set to 3

/* output
10:54:34.748 App Three 0123┃ level0
10:54:34.748 App Three 0123┃ level3
*/

API

new ConCol(appName, color, levelShow)

Creates a new logger instance.

• appName (string): the application/namespace name (optional)
• color (string): base text color: black, red, green, yellow, blue, magenta, cyan, white, gray (default: white)
• levelShow (number): the maximum log level to output, so 0 is silent/important only (default: Infinity - shows everything)

The following methods are available.

log(msg, level)

Outputs console.log() messages.

• msg (undefined|string|Array): the message (optional)
• level (string|Array): message logging level (default 0)

The msg can be any of:

• a string
• a string with carriage returns (outputs to separate lines)
• a [name, value, unit] array, e.g. ['errors', 0, ' found']
• an array containing strings or [name, value, unit] arrays

info(msg, level)

Outputs console.info() messages. Parameters are identical to log().

warn(msg, level)

Outputs console.warn() messages prefixed with "WARN:". Parameters are identical to log().

error(msg, level)

Outputs console.error() messages prefixed with "ERROR:". Parameters are identical to log().

Advanced configuration

The following static properties configure log layout:

• ConCol.appSize = <num> - the width of the appName column (default 14)
• ConCol.nameSize = <num> - the width of a name column (30)
• ConCol.valueSize = <num> - the width of a value column (10)
• ConCol.numFormat = <Intl.NumberFormat> - numeric value object (#,### rounded to 0dp)
• ConCol.timeFormat = <Intl.DateTimeFormat> - date/time object (HH:MM:SS.mmm)

// example
ConCol.appSize = 7;
ConCol.nameSize = 15;
ConCol.valueSize = 10;

// show values in #,###.## format
ConCol.numFormat = new Intl.NumberFormat(
  'en-US',
  { minimumFractionDigits: 2, maximumFractionDigits: 2 }
);

// show dates in DD/MM HH:MM:SS format
ConCol.timeFormat = new Intl.DateTimeFormat(
  'af-AF',
  {
    month: '2-digit', day: '2-digit',
    hour: '2-digit', minute: '2-digit', second: '2-digit'
  }
);

const cc = new ConCol('App One', 'yellow');

cc.log([ 'number two', 12345.678 ]);
cc.log([ 'number one', 123 ]);

/* output
05-06 13:18:20 App One┃      number two:  12,345.68
05-06 13:18:20 App One┃      number one:     123.00
*/