Loggerr


A very simple logger.

Features:

- Synchronous output (great for cli's, browser and tools)
- Levels (built-in and customizable)
- Formatting (built-in and customizable)
- Loggerr is dependency free (formatters are not)
- Always captures stack trace on error logs
- Tiny filesize
- The cli formatter 🚀

!cli formatter example

Install

``
$ npm install --save loggerr
`

Usage

`javascript
const log = require('loggerr')
log.error(new Error('My error message'))
// Thu Apr 16 2015 22:05:27 GMT-0500 (CDT) [error] - {"msg":"Error: My error message\n"}

log.info('Something happened', {
foo: 'info about what happened'
})
// Thu Apr 16 2015 22:05:27 GMT-0500 (CDT) [info] - {"msg":"Something happened","foo":"info about what happened"}
`

Log Levels

Each log level can be directed to a different output stream
or disabled entirely. The default levels are as follows:

- emergency
- alert
- critical
- error
- warning (default)
- notice
- info
- debug

Constants are available for setting and referencing the levels and
their streams. These constants are the all uppercase version of the
level. Here is an example of setting the log level:

`javascript
const logger = new Loggerr({
level: Loggerr.DEBUG
})

logger.debug('Foo')
// Thu Apr 16 2015 22:05:27 GMT-0500 (CDT) [debug] - {"msg":"Foo"}
`

$3

You can fully customize the levels for your purposes. For example, here
we implement pino compatible levels:

`javascript
const log = new Loggerr({
level: [ 'trace', 'debug', 'info', 'warn', 'error', 'fatal' ]
})

log.trace('Example trace log')
`

See the example of custom levels for cli output.

Log Formatting

Loggerr supports formatting via formatter functions. The default
formatter outputs a timestamp, the log level and the messages formatted
as json. But you can provide a custom formatter function with the formatter
options. Formatter functions take three parameters: date, level, data.
Say we want to output the log message with a color based on the level:

`javascript
const Loggerr = require('loggerr')
const chalk = require('chalk')

const logger = new Loggerr({
formatter: (date, level, data) => {
var color
switch (Loggerr.levels.indexOf(level)) {
case Loggerr.EMERGENCY:
case Loggerr.ALERT:
case Loggerr.CRITICAL:
case Loggerr.ERROR:
color = chalk.red
break
case Loggerr.WARNING:
case Loggerr.NOTICE:
color = chalk.yellow
break
case Loggerr.INFO:
case Loggerr.DEBUG:
color = chalk.white
break
}
return color(data.msg)
}
})
`

There are a few built-in in formatters:

- default: Outputs date, level and json
- cli: Outputs the message and json data, colorized and formatted
- bunyan: Compatible format to bunyan
- browser: Relies on console.log, so just returns the data

For these built-in formatters can specify the string name of the formatter for built-in formatters:

`javascript
const log = new Loggerr({
formatter: 'cli'
})
`

To use the cli formatter you can require it and pass the formatter options:

`javascript
const log = new Loggerr({
formatter: require('loggerr/formatters/cli')
})
`

$3

If you need to write raw logs without formatting there are two options:

1. writeLevel(level, msg, done): Will respect logging level but skip all formatting
2. write(level, msg, done): Will write logs regardless of level and skip all formatting

Output Streams

You can output each level to it's own stream. The method is simple, just pass an
array of streams corresponding to each level as the streams option. The simplest
way is to just map over Loggerr.levels, this is how we set the defaults:

`javascript
new Loggerr({
streams: Loggerr.levels.map(function (level, i) {
return i > Loggerr.WARNING ? process.stdout : process.stderr
})
})
`

The most useful reason to specify an output stream to to redirect logs to files.
Here is an example of how to do that:

`javascript
const logfile = fs.createWriteStream('./logs/stdout.log', {
flags: 'a',
encoding: 'utf8'
})

new Loggerr({
streams: Loggerr.levels.map(() => logfile)
})
`

$3

You can also pass a debugStream which will receive all logs regardless of level. This is helpful when you want to send
logs to a file which you can use in error reporting or debugging failures.

`javascript
new Loggerr({
debugStream: fs.createWriteStream('./logs/debug.log', {
flags: 'a',
encoding: 'utf8'
})
})

`

Bundling with Rollup

There is a dynamic require in this library. If you intend to use this with a bundler (ex Rollup) you may need to configure it to include the correct formatter if you pass that
option as a string (ex formatter: 'cli').

Example:

`javascript
// rollup.config.js
const { nodeResolve } = require('@rollup/plugin-node-resolve');
const commonjs = require('@rollup/plugin-commonjs');

module.exports = {
input: 'index.js',
output: {
file: 'bundle.js',
format: 'commonjs'
},
plugins: [
nodeResolve(),
commonjs({
dynamicRequireTargets: [
'./node_modules/loggerr/formatters/cli.js',
]
})
]
};
`

The values above will change based on your application, but the main important thing is the dynamicRequireTargets configuration.

Contributing

Contributions are welcome! To get started contributing, ensure you have a modern Node.js version and run node --run
setup. To run the tests run npm t, and to run the lint npm run lint [-- --fix]`. When pushing commits, kindly use
Conventional Commits but I will be sure to clean things up before we
merge.