flogger-log

Flogger

A ready to use - zero conf - logger

Install

npm install --save 'flogger-log'

Basic usage

import Flogger from 'flogger-log';

const flog = new Flogger();
flog.$debug('Something important');
flog.$error('Watch out!');

And it's customizable too!

You can change log levels (defaults are trace, debug, info, warning and error) and how events are recorded passing options to Flogger constructor.
The FileRenderer renderer, which saves events to file, is shipped with this package.

import { Flogger, FileRenderer } from 'flogger-log';

// Use the shipped FileRenderer for saving log to file.
const flog = new Flogger({
  // Custom log levels, from less critical (left) to more critical (right)
  levels: ['foo', 'bar', 'tic', 'tac'],

  // Current minimum log level.
  // We are not going to log any event less critical than 'bar' (sorry foo...)
  level: 'bar',

  // Pass a FileRenderer instance to flogger
  renderer: new FileRenderer({ path: 'logfile.txt' })
});

// Use custom log functions (custom log levels)
flog.$bar('This will be logged');
flog.$foo('This will NOT');

// Or use the log() function directly
flog.log('hello', 'tic');
flog.log('world', 'tac');

Methods

Every log level name will have a corresponding method exposed by the flog object. Calling one of these function will results in a corresponding log record to be stored by the renderer (according to your current log level).

The methods are named '$' followed by the log level name and accept log data as the only argument.

example:
flog.$debug(<data>) for 'debug'
flog.$foo(<data>) for 'foo'

The special method log(levelName, data) can be use in place of the '$' methods. It accepts the log level name as the first argument and the log data as the second argument.

You can write your custom renderer

A flogger renderer is just a object exposing a "render" function.
The render function will receive three arguments, the level name, the origin of the event and the data passed to the log function.

In the simplest case the renderer is really just a plain object with a function. This is how the console renderer is implemented:

export default {
  render(level, origin, message) {
    const timeDate = new Date().toUTCString();
    console.log(`${timeDate} - [${level}] ${origin}:`);
    console.log(message);
    console.log();
  },
}

The console renderer is included in this package and it's the default one if you don't specify one in the Flogger constructor options.

Advanced renderers

More advanced renderers could be written as classes accepting options in their constructors for fine-grained customization.

File renderer

The FileRenderer is a renderer for writing classic log files and it is shipped with this package.

import { Flogger, FileRenderer } from 'flogger-log';

const flog = new Flogger({
  renderer: new FileRenderer(options)
});

The file renderer constructor accepts this options argument:

{
  path,
  fileSizeLimit,
  fileSizeOverflowPolicy,
  archiveNamesSorting,
}

path: String

The log file path.

fileSizeLimit: Integer >= 0, default: 0

The file size threshold limit in bytes.
When a log file size gets over this limit, on the next log function call the policy associated to the fileSizeOverflowPolicy option will be applied.
Set to 0 for "no limit".

fileSizeOverflowPolicy: 'archive' or 'overwrite', default: 'archive'

Policy to be applied when the log file gets over the value of fileSizeLimit option.
Set to overwrite for writing over the existing log file.
Set to archive to make archive copies of the log file.
When archive is used, the archived filename will be:

<log_filename_without_extension>_<suffix>.<log_filename_extension>

Where suffix is an integer between 1 and 10000.
By default newer archive files gets higher suffix number (descending order). You can change this behaviour with the archiveNamesSorting option.

archiveNamesSorting: 'descending' or 'ascending', default: 'descending'

The archiveNamesSorting change the way suffixes are assigned to archive file names.
Set to descending to assign higher suffix numbers to newer archive files.
Set to ascending to assign lower suffix numbers to newer archive files.

ChangeLog

• 1.2.0 | The trace level was added to the default ones.

• 1.1.0 | Support for archiving log files when their size gets over a threshold was added to FileRenderer.

License

MIT License

Copyright (c) 2018 Valerio Bianchi

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.