UniversalLog

Flexible logger for Node.js and the browser.

Installation

npm install --save universal-log

Usage

import UniversalLog from 'universal-log';

let logger = new UniversalLog({ appName: 'example' });

logger.info('Little info');
logger.error('There is something wrong');

Concepts

Levels

There are 10 levels of logging: silence, trace, debug, info, notice, warning, error, critical, alert and emergency.

Depending on the type of output, a level can have an effect on the way a log message is formated. For example, the ConsoleOutput uses different colors for each levels.

A muteLevels option allows to mute some levels. By default, the silence level is muted. The trace and debug levels are also muted when NODE_ENV is undefined or equal to 'development'.

Outputs

You can configure where you want to output your log messages.

For now, the supported outputs are:

• ConsoleOutput writes logs to Node.js or browser console.
• RemoteOutput sends logs to a UniversalLogServer.
• AWSCloudWatchLogsOutput sends logs to AWS CloudWatch Logs.

It is easy to create your own type of output. An output is just an object with a write(logName, hostName, level, message) method. See an example of custom output.

API

new UniversalLog([options])

Create a logger.

import UniversalLog from 'universal-log';

let logger = new UniversalLog({ appName: 'example' });

options

• logName: the name of the log. If not specified, the name is a combination of appName and NODE_ENV.
• appName: the name of the running application.
• hostName: the name of the host where the application is running. If not specified, hostName is determined from the hostname of the machine. If the application is running in a browser, hostName defaults to 'browser'.
• outputs: the outputs where all the logging goes. The default is an instance of ConsoleOutput.
• muteLevels: mute the specified levels. By default, the silence level is muted. The trace and debug levels are also muted when NODE_ENV is undefined or equal to 'development'.
• decorators: a simple way to "decorate" log messages. A decorator is a function receiving a string (a log message) and returning a string (the decorated log message). Decorators are useful to add some contextual information to log messages. For example, a decorator could be used to add the name of the current user.

logger.log(level, messsage)

Log a message with the specified level.

logger.log('info', 'Little info');
logger.log('warning', 'There is something wrong');

logger.{level}(messsage)

Convenient shorthand methods to log messages for a specific level.

logger.debug('Little info');
logger.error('There is something wrong');
logger.warning('Be careful, something is happening');

logger.createTimer([label])

Measure and log the time passed doing something.

let timer = logger.createTimer('Heavy computation');
// ...
timer.stop();

logger.addOutput(output)

Add an output to the logger.

import { RemoteOutput } from 'universal-log';

logger.addOutput(new RemoteOutput('http://api.example.com/v1'));

logger.addDecorator(decorator)

Add a decorator to the logger.

logger.addDecorator(function(message) {
  return message + ` (current user: ${username})`;
});

License

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