logbok

To install

npm install --save logbok

To create a logger for a class

export class MyClass {
    ...
    private static readonly logger = Logbok.getLogger(MyClass);
    ...
}

Or for a vanilla javascript function

...
var logger;

function myFunction() {
    ...
    logger = logger || Logbok.getLogger(myFunction);
    ...
}
...

To log specific messages

logger.debug('this is a debug log');
logger.info('this is an info log');
logger.warn('this is a warn log');
logger.error('this is an error log');

Configurations

Logbok reads the specified configuration from its CONFIG property.
Currently supported configurable parameters are log-level, disabled-loggers, and log-appenders.

ATTRIBUTE	TYPE	DESCRIPTION	SAMPLE USAGE***
log-level	string	can be either debug, info, warn, and error - with debug as the lowest and error as the highest level, respectively - initially set to debug.	Logbok.CONFIG['log-level'] = 'debug'
disabled-loggers	array	contains the list of the classes/types whose loggers will be disabled - initially set to empty.	Logbok.CONFIG['disabled-loggers'] = [MyClass]
log-appenders	array	contains the list of instances of log appenders to be used - initially set to empty. Currently, Logbok provides 5 appenders, namely, ConsoleLogAppender, ChromeConsoleLogAppender, NodeConsoleLogAppender, IsoTimestampAppender, and RollingFileAppender	Logbok.CONFIG['log-appenders'] = [ new ChromeConsoleLogAppender(), new CustomLogAppender() ]

***Note: All of the above mentioned attributes are configured in a way that when a new value is assigned, the changes will be applied immediately.

Creating a custom log appender

If the provided appenders are insufficient, you can extend those and/or make your own log appender for your own specific usecase.
You just need to implement the Appender interface like below:

// this is a blunt angular sample for a remote log appender implementation
export class RemoteLogAppender implements Appender {
    readonly appenderName = 'RemoteLogAppender';
    private static readonly chromeConsoleLogAppender = new ChromeConsoleLogAppender();

    log(logEntry: LogEntry): void {
        const message = logEntry.buildLogString('');
        this.http.post('https://log/service/url', message, /*httpOptions*/).subscribe(() => {
            this.chromeConsoleLogAppender.log(logEntry);
        });
    }
}
...
// then somewhere up the initialization phase
Logbok.CONFIG['log-appenders'] = [ new RemoteLogAppender() ]

For reference purposes, the appender interface is defined in Logbok as

export interface Appender {
    readonly appenderName: string;
    log(logEntry: LogEntry): void;
}

Sample Codes

Vanilla javascript code snippet for Node JS:

var { Logbok, ConsoleLogAppender } = require("logbok");

var logger;

function myFunction() {
   logger = logger || Logbok.getLogger(myFunction);
   logger.info('this is an info log');
}

Logbok.CONFIG['log-appenders'] = [new ConsoleLogAppender()]

myFunction(); // prints something like "04/24/2019 - 15:30:29.958 INFO [myFunction] - this is an info log"

Code snippet for Typescript:

import { Logbok, ConsoleLogAppender } from "logbok";

export class MyClass {
    private static readonly logger = Logbok.getLogger(MyClass);

    log() {
        MyClass.logger.info('this is an info log');
    }
}

Logbok.CONFIG['log-appenders'] = [ new ConsoleLogAppender() ];
new MyClass().log(); // prints something like "04/24/2019 - 15:46:33.891 INFO [MyClass] - this is an info log"

Log Appenders

Logbok comes with 5 core log appenders, namely, ConsoleLogAppender, ChromeConsoleLogAppender, NodeConsoleLogAppender, IsoTimestampAppender, and RollingFileAppender. Each one has a different usecase but some can be used in conjunction with one another (e.g. RollingFileAppender can be paired with either of the three: ConsoleLogAppender, NodeConsoleLogAppender, IsoTimestampAppender).

• ConsoleLogAppender

  This is the most basic log appender among all logbok appenders.
  This one is built on top of the console object, hence the name.
  No magic and all, just plain text pre-formatted to look like a decent log message.
  Below is a sample snippet of the output of a ConsoleLogAppender.

  

• IsoTimestampAppender

  This one is time-formatted version of ConsoleLogAppender.
  No magic and all, just plain text with pre-formatted time to look like a decent log message.
  Below is a sample snippet of the output of a IsoTimestampAppender.

  

• ChromeConsoleLogAppender

  This one is a color-coded version of ConsoleLogAppender dedicated for Chrome/Chrome-based renderer apps (e.g. Electron)
  Below is a sample snippet of the output of a ChromeConsoleLogAppender.

  

• NodeConsoleLogAppender

  This one is similar to ChromeConsoleLogAppender in the manner that it is also a color-coded version of ConsoleLogAppender.
  The only difference is that this one is for the command line/terminal window console instead of the chrome.
  Below is a sample snippet of the output of a NodeConsoleLogAppender.

  

• RollingFileAppender

  This one is more advanced compared to the other types of appender. The idea is that it redirects logs to a file instead of using a console object.
  Currently, this can only be used by backend codes, as it requires collocation of the log file with the running instance.
  This appender can be instantiated with the following optional parameters:

  NAME	TYPE	DESCRIPTION	REMARKS
  filePath	string	the path of the file where to write the logs, creates it if it does not exist yet	default value is './logbok.log'
  rolloverOption	RolloverOption	the rollover mechanism describing when to rename the current log file with a new rollover filename. see below description of possible values	naming follows counting numbers starting from 1, e.g. for filepath='./server.log' rollover files will be server-1.log, server-2.log, and so on.

   export declare interface RolloverOption {
       size?: RolloverSize,
       sizeInKiB?: number
       sizeInMiB?: number,
       sizeInGiB?: number,
       timeInterval?: RolloverTime,
       timeIntervalInSeconds?: number,
       timeIntervalInMinutes?: number,
       timeIntervalInHours?: number
   }
  
   export enum RolloverTime {
       HOURLY,
       DAILY,
       WEEKLY,
       MONTHLY
   }
  
   export enum RolloverSize {
       TEN_MiB, // is equal to (10 * 1024 * 1024) bytes
       FIFTY_MiB, // is equal to (5 * TEN_MiB) bytes
       HUNDRED_MiB, // is equal to (10 * TEN_MiB) bytes
       ONE_GiB, // is equal to (10 * 1024 * 1024 * 1024) bytes
       TEN_GiB // is equal to (10 * TEN_GiB) bytes
   }
  

  Below are sample rollover configurations

   new RollingFileAppender('./server.log', { size: RolloverSize.TEN_MiB })       // rolls over everytime log file reaches 10MiB
   new RollingFileAppender('./server.log', { sizeInKiB: 100 }                    // rolls over everytime log file reaches 100KiB
   new RollingFileAppender('./server.log', { timeInterval: RolloverTime.HOURLY } // rolls over every 1 hour
   new RollingFileAppender('./server.log', { timeIntervalInSeconds: 10 }         // rolls over every 10 seconds