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    2.0.1 • Public • Published

    logbro · Codeship badge

    There were no good names left for logging libraries, so I chose a terrible one instead.

    const bro = require('logbro');
    bro.warn('I have a terrible name, but I make pretty logs');


    • Pretty (default), JSON, and custom formats
    • Configurable stdout and stderr streams
    • Singleton by default
    • Shared or local format and level
    • Error stack serialization



    • trace
    • debug
    • info


    • warn
    • error
    • critical

    Each value implicitly includes all levels above itself – so, for example, when your app is run with NODE_DEBUG=warn node app.js, all warn, error, and critical logs will be sent to stdout/stderr. In the same example, and bro.debug() would effectively be no-ops.


    bro.log(level, message, [...interpolationValues])

    • level (string): one of the levels defined above
    • message (string): an optional message. If the message is a format string, it will use the interpolationValues as the format parameters.
    • [...interpolationValues] (...any): optional values to use to format the message using util.format(). Otherwise, these values will be appended to the message.

    bro.<level>(message, [interpolationValues])

    The same as bro.log, but without the need to pass the level as a parameter. Prefer using these to bro.log.

    bro.format (Log => string)

    Get the current log format OR set the current log format for this bro instance. By default, a bro instance will use the shared log format. Set bro.format = null to resume using the shared log format.


    • timestamp (string)
    • level (string)
    • message (string | undefined)

    Logbro.level (string)

    Get the shared log level OR set the shared log level.

    Logbro.format (Log => string)

    Get the shared log format OR set the shared log format.

    new Logbro(opts)

    • [format] (string | (Log => string))
    • [stdout] (stream.Writable)
    • [stderr] (stream.Writable)
    bro.log('info', 'This is an info log');
    // Preferred'This is another info log');

    NOTE: bro.log has the same argument signature as console.log.


    Log Level

    logbro will read the initial log level from the NODE_DEBUG environment variable.

    The NODE_DEBUG environment variable can actually contain multiple flags, but the one with the lowest priority level will win. For example, NODE_DEBUG=debug,info,critical node app.js will use debug as the log level, since it automatically includes the other levels.

    NOTE: If the log level is not set, logbro will not write any logs.

    Log Format

    logbro will read the initial log format from the LOGBRO_FORMAT environment variable.

    Possible formats:

    • pretty
    • json


    Each log level will emit an event of the same name if the log level is high enough. For example, bro.critical('foo'); will emit a 'critical' event whose callback argument will be of type Log.

    This way, applications can hook in to the logging system and respond however they want (post to Slack, send to a logging service, etc.).


    By default, logs are written to either process.stdout or process.stderr.

    Apps can optionally overwrite bro.stdout and bro.stderr with other instances of stream.Writable in order to stream logs to the filesystem, via HTTP, to a database, etc.

    Node.js Compatibility

    logbro requires >= Node.js 8.3.


    const bro = require('logbro');
    bro.critical( 'this is a %s with some %s', 'log', 'formatting' );
    Event binding
    const bro = require('logbro');
    bro.on( 'critical', msg => slack.notify( msg ) );
    bro.on( 'error', (msg, log) => {
    const bro = require('logbro'),
    const fs  = require('fs'),
    const file = fs.createWriteStream('./log.txt');
    bro.stdout = file;
    bro.stderr = file;
'blah blah blah');
    Custom Logbro Instance
    const { Logbro } = require('logbro')
    const format = log => '>> ' + log.message || 'No message';
    const logger = new Logbro({ format });'Hello world'); // ">> Hello world"


    npm i logbro

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