// To use the logging utilities
const logging = require('logging-utils');

// Valid logging levels
const LogLevel = logging.LogLevel; 

// Logging configuration functions
const isLoggingConfigured = logging.isLoggingConfigured;
const configureLogging = logging.configureLogging;

// Convenience logging function
const log = logging.log;

Provide a context object on which to configure logging, e.g:

const context = {}; // replace with your own target object to be configured

Configure logging on the context object

To configure default logging on an existing object (WITHOUT overriding any existing logging on context)

configureLogging(context);
// which is equivalent to:
configureLogging(context, {logLevel: LogLevel.INFO});

To configure WARN level logging on an existing object (WITHOUT overriding any existing logging on context)

configureLogging(context, {logLevel: LogLevel.WARN});

To configure specific logging (WITHOUT overriding any existing logging on context)

const settings = {logLevel: LogLevel.DEBUG, useLevelPrefixes: false, useConsoleTrace: false, underlyingLogger: console}; // or your own settings
configureLogging(context, settings);
// OR with explicit forceConfiguration false
configureLogging(context, settings, undefined, false);

To configure specific logging (OVERRIDING any existing logging on context!)

configureLogging(context, settings, undefined, true);

To configure default logging on a new object

const log = configureLogging({});

To configure default logging on an existing object with overriding options and forceConfiguration true

configureLogging(context, undefined, options, true);
// Alternatively ...
configureLogging(context, options, undefined, true);

To configure default logging on an existing object with overriding options, an explicit logger and forceConfiguration true

const options = undefined; // ... or any LoggingOptions you want to use to partially or fully override the default logging settings
configureLogging(context, {underlyingLogger: console}, options);
const CustomLogger = {/* ... */}; // implement your own custom logger if required
configureLogging(context, {underlyingLogger: CustomLogger}, options, true);

To configure logging from options

const options = { logLevel: LogLevel.DEBUG, useLevelPrefixes: true, useConsoleTrace: false }; // replace with your own options
configureLogging(context, undefined, options);
// OR just ...
configureLogging(context, options);

To configure logging from EITHER logging settings OR logging options (OR defaults if neither) - WITHOUT overriding any existing logging on context

configureLogging(context, settings, options);
// OR with explicit forceConfiguration false ...
configureLogging(context, settings, options, false);

To configure logging from EITHER logging settings OR logging options (OR defaults if neither) - OVERRIDING any existing logging on context!

configureLogging(context, settings, options, true);

To OVERRIDE any pre-configured logLevel setting or option during runtime configuration, set a logging level on the environment variable named by the envLogLevelName setting, which is also configurable and defaults to 'LOG_LEVEL'. Any valid logLevel found with process.env[envLogLevelName] will take precedence over any other logLevel setting or option.

// For unit testing, set the `LOG_LEVEL` environment variable programmatically
process.env.LOG_LEVEL = LogLevel.DEBUG;

// Alternatively, if you configured your own `envLogLevelName` as 'MyLogLevel', e.g.
configureLogging(context, {envLogLevelName: 'MyLogLevel'});
// then for unit testing, set your `MyLogLevel` environment variable programmatically
process.env.MyLogLevel = LogLevel.TRACE;

2. Log messages

To log errors:

// Log an error with a strack trace
context.error('Error message 1', new Error('Boom'));

// Log an error without a stack trace
context.error('Error message 2');

To log warnings:

// Log a warning (or do nothing when warnings are disabled)
context.warn('Warning message 1');

// To avoid building the warning message (when warnings are disabled)
if (context.warnEnabled) context.warn('Warning message 2');

To log info messages:

// Log an info message (or do nothing when info messages are disabled)
context.info('Info message 1');

// To avoid building the info message (when info messages are disabled)
if (context.infoEnabled) context.info('Info message 2');

To log debug messages:

// Log a debug message (or do nothing when debug messages are disabled)
context.debug('Debug message 1');

// To avoid building the debug message (when debug messages are disabled)
if (context.debugEnabled) context.debug('Debug message 2');

To log trace messages:

// To log a trace message (or do nothing when trace messages are disabled)
context.trace('Trace message 1');

// To avoid building the trace message (when trace messages are disabled)
if (context.traceEnabled) context.trace('Trace message 2');

To log messages at a specified log level (using the log method):

// To log a message at LogLevel.TRACE (or do nothing when trace messages are disabled)
context.log(LogLevel.ERROR, 'Error message 1', new Error('Boom'));

// Note that this will also work with console, but you won't get any suppression according to log level
console.log(LogLevel.TRACE, 'Trace message 1');

To log messages at a specified log level (using the log function):

// Alternatively using log function
log(context, LogLevel.DEBUG, 'Debug message 1');

// Note that this will also work with console (and undefined), but you won't get any suppression according to log level
log(console, LogLevel.WARN, 'Warn message 1');
log(undefined, LogLevel.ERROR, 'Error message 1', new Error('Boom 2'));

Unit tests

This module's unit tests were developed with and must be run with tape. The unit tests have been tested on Node.js v4.3.2.

See the package source for more details.

Changes

See release_notes.md

4.0.19

Renamed dummy first exports (exports._ = '_'; //IDE workaround) of most modules to (exports._$_ = '_$_';) to avoid potential future collisions with lodash & underscore
Updated core-functions dependency to version 3.0.19

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Package last updated on 20 Nov 2017

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