Balsa

Lightweight, multi-relay JavaScript logging for the browser

Balsa is a lightweight, multi-relay logging library designed for use in the browser. It includes a relay for consistent, cross-browser JavaScript console logging, as well as an AJAX relay to send log messages to logging servers.

Prerequisites

An environment that supports the CommonJS module pattern (require, module, exports, etc.), e.g., Node.js, but it really shines when bundled with Browserify and used in the browser.

Basic Usage

// Create a new Balsa logger with a console relay
var balsa = new require( 'balsa' )( {
    relays: [
        new require( 'balsa/relay/console' )()
    ]
} );

// Start loggin'!
balsa.debug( 'Debug message' );
balsa.log( 'General log message' );
balsa.info( 'Info message' );
balsa.warn( 'Warning message' );
balsa.error( 'Error message' );

Initialization

To begin using Balsa, you must first import it with require, and create a new instance.

var balsa = new require( 'balsa' )();

You may configure Balsa during instantiation as in the following example.

Please note that all configuration is optional and the following represents the default value of each optional configuration item.

var balsa = new require( 'balsa' )( {

    /**
     * Enable/disable logging. May be modified post-initialization via
     * `.enable()` and `.disable()`
     */
    enable: true,

    /**
     * Logging prefix that will be prepended to each log message, e.g., [myApp]
     */
    prefix: null,

    /**
     * Define default minimum logging level, i.e., don't log messages below the
     * specified level. If `null`, all levels will be logged. Possible values
     * are:
     *     - null    - Log ALL THE THINGS
     *     - 'debug' - Don't log below debug (lowest level, log everything)
     *     - 'log'   - "     "   "     log
     *     - 'info'  - "     "   "     info
     *     - 'warn'  - "     "   "     warn
     *     - 'error' - "     "   "     error
     *
     * Relays may override this value in their own configuration.
     */
    minLevel: null,

    /**
     * Define the message format. Available variables are:
     *
     *     - `$TIMESTAMP` - Timestamp of the log, in [ISO 8601](http://en.wikipedia.org/wiki/ISO_8601)
     *     - `$LEVEL`     - The logging level
     *     - `$PREFIX`    - The message prefix
     *     - `$MESSAGE`   - The message body
     *
     * Relays may override this value in their own configuration.
     */
    messageFormat: '$TIMESTAMP $LEVEL\t$NAMESPACE\t$MESSAGE',

    /**
     * Add relays, e.g.,
     *
     *     relays: [
     *           new require( 'balsa/relay/console' )(),
     *           new require( 'balsa/relay/ajax' )( {
     *               host: 'log.example.com',
     *               port: 1234
     *           } )
     *       ];
     */
    relays: [];
} );

API

After initialization, you may use any of the following functions.

balsa.{debug, log, info, warning, error, etc.}( message )

Log a message at the specified level. There are 4 available levels, from most to least severe:

1. debug
2. log
3. info,
4. warning, warn
5. error, err

balsa.debug( 'Debug message' );

balsa.log( 'General message' );

balsa.info( 'Info message' );

balsa.warning( 'Warning message' );
balsa.warn( 'Also a warning message' );

balsa.error( 'Error message' );
balsa.err( 'Also an error message' );

balsa.enable()

Enable logging.

balsa.enable();

balsa.disable()

Disables all logging.

balsa.disable();

balsa.prefix( prefix )

Set the prefix that will be prepended to every log message.

// Prefix all messages with '[myApp]'
balsa.prefix( '[myApp]' );

balsa.minLevel( minLevel )

Sets the minimum default level message that will be logged. If 'all', all levels will be logged.

Note that relays may define their own min level, which will override this value for those relays.

// Only log warnings and below (error)
balsa.minLevel( 'warn' );

balsa.messageFormat( messageFormat )

Sets the format each message will be outputted as. Available variables are:

• $TIMESTAMP - Timestamp of the log, in ISO 8601
• $LEVEL - Level of the message
• $PREFIX - The message prefix
• $MESSAGE - The message body

// Configures the message format, e.g.,
// 2014-09-30T18:58:45+08:00, warn [myApp], Log message
balsa.messageFormat( '$TIMESTAMP, $LEVEL, $PREFIX, $MESSAGE' );

balsa.add( relay )

Adds a new relay to the logger.

// Adds an AJAX relay with a custom level, a host, and a port.
balsa.add( new require( 'balsa/relays/ajax' )( {
    minLevel: 'error',
    endpoint: 'logs.example.com'
} ) );

balsa.remove( relay )

Removes a relay from the logger.

// Create a new AJAX relay
var ajaxRelay = new require( 'balsa/relays/ajax' )( {
    minLevel: 'error',
    endpoint: 'logs.example.com'
} )

// Add relay
balsa.add( ajaxRelay );

// Remove relay
balsa.remove( ajaxRelay );

Relays

Relays are where your log messages get sent to. You can attach 0 or more relays to any Balsa instance.

Relay configuration

All relays may define their own min levels, e.g., one relay may log messages of all levels, and another may log only error-level messages.

All relays may also define their own message formats, e.g., one relay may format its messages with a timestamp, and another relay may choose to omit the timestamp.

// Add a new console relay that logs all levels, and has a message format of
// `$PREFIX: $MESSAGE`
balsa.add( new require( 'balsa/relays/console' )( {
    minLevel:       null,
    messageFormat:  '$PREFIX: $MESSAGE'
} ) );

Core relays

Balsa comes with two relays, console and ajax.

console

A cross-browser relay. Uses the browser's build-in JavaScript console functions or if the console object does not exist, the logger will fail silently to prevent runtime errors.

balsa.add( new require( 'balsa/relays/console' )() );

ajax

An AJAX relay. Allows you to make an AJAX call to a REST service. Two configuration options, host and port are required, but type is optional.

balsa.add( new require( 'balsa/relays/ajax' )( {
    // URL string of the endpoint to log to
    endpoint: 'logs.example.com',
} ) );

Custom relays

You may also make your own relays. Use the core relays as examples, and require them as you would a core relay.

Reference

• Apache log4j
• winston
• minilog