@novice1/logger

A JavaScript logging utility that prefixes logs and colors them if stdout/stderr is a TTY. Works in Node.js.

Installation

$ npm install @novice1/logger

Usage

Once imported use the function as it is or use its methods to log.

Example:

let logger = require('@novice1/logger');

// white
logger('simple log'); 
logger.log('simple log');

// blue
logger.info('info log');

// magenta background
logger.debug('debug log');

// yellow
logger.warn('yellow log');

// red
logger.error('error log');

You can also chose your own colors for the logs using the methods print and println. Available colors can be found in the property colors.

Example:

let logger = require('@novice1/logger');

// green
logger.print(logger.colors.FG_GREEN, 'green', 'message');

// blue background
logger.println(logger.colors.BG_BLUE, 'blue background', 'message');

Available colors

• RESET
• BRIGHT
• DIM
• UNDERSCORE
• BLINK
• REVERSE
• HIDDEN
• FG_BLACK
• FG_RED
• FG_GREEN
• FG_YELLOW
• FG_BLUE
• FG_MAGENTA
• FG_CYAN
• FG_WHITE
• BG_BLACK
• BG_RED
• BG_GREEN
• BG_YELLOW
• BG_BLUE
• BG_MAGENTA
• BG_CYAN
• BG_WHITE

Methods

• error: (...args: any[]) => void
• warn: (...args: any[]) => void
• info: (...args: any[]) => void
• log: (...args: any[]) => void
• debug: (...args: any[]) => void
• silly: (...args: any[]) => void
• println: (colorCode: int, ...args: any[]) => void
• print: (colorCode: int, ...args: any[]) => void

Levels

Methods can print logs depending on the level of the logger. Levels are available in the property levels.

By priority:

• error
• warn
• info
• log / verbose
• debug
• silly

Example:

let logger = require('@novice1/logger');

// set level to info
logger.setLevel(logger.levels.info);

// will print
logger.info('info log');

// will print
logger.warn('warn log');

// will not print
logger.print(logger.colors.FG_GREEN, 'green', 'message');

Using with debug

It can be used with the package debug. All you have to do call the method debugger sending a namespace as parameter. That will return a function with the available methods except for print and println.

debug properties and methods are available from the property Debug.

Example:

// enable 'app:*'
require('@novice1/logger').Debug.enable('app:*');

let logger = require('@novice1/logger').debugger('app:log');
logger('simple log'); 
logger.log('simple log');
logger.info('info log');
logger.debug('debug log');
logger.warn('yellow log');
logger.error('error log');

You can also extend debugger

// enable 'auth:*'
require('@novice1/logger').Debug.enable('auth:*');

let logger = require('@novice1/logger').debugger('auth');

// extend namespace
const logSign = logger.extend('sign');
const logLogin = logger.extend('login');

logger('hello'); // auth log : hello
logSign('hello'); //auth:sign log : hello
logLogin('hello'); //auth:login log : hello

Formatters

printf-style formatting can be used when using with debug.

Officially supported formatters:

Formatter	Representation
%O	Pretty-print an Object on multiple lines.
%o	Pretty-print an Object all on a single line.
%s	String.
%d or %i	Number (both integer and float).
%j	JSON. Replaced with the string '[Circular]' if the argument contains circular references.
%%	Single percent sign ('%'). This does not consume an argument.

Other formatters:

Formatter	Representation
%P	Print an Object on multiple lines.
%p	Print an Object on a single line.

Custom logger

You can create a custom logger, assign its own level, print function (= write) and more.

Example:

const Logger = require('@novice1/logger');

// create custom logger
const customLogger = Logger.createLogger({
  levels: {
    success: {
      // color of message.
      color: Logger.colors.FG_GREEN, 
      // level. Default: Logger.levels.silly
      level: Logger.levels.info 
    }
  },
  /**
   * Overwrite the default function to print.
   * Could be used to customize message, write in a file, etc ...
   */
  write({ args, level, message, prefixText }) {
    console.log(`custom ${prefixText} - ${message} !`);
  }
});

// print objects on a single line
customLogger.singleLine = true;

// set level
customLogger.level = Logger.levels.log;

// will not print because of level set
customLogger.debug('debug log');

// will print
customLogger('simple log'); 
customLogger.log('simple log');
customLogger.info('info log');
customLogger.warn('warning log');
customLogger.error('error log');

// custom level print
customLogger.custom('success',  'everything is good');