winston

# winston

A logger for just about everything.

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## winston@3

See the [Upgrade Guide](UPGRADE-3.0.md) for more information. Bug reports and
PRs welcome!

## Looking for `winston@2.x` documentation?

Please note that the documentation below is for `winston@3`.
[Read the `winston@2.x` documentation].

## Motivation

`winston` is designed to be a simple and universal logging library with
support for multiple transports. A transport is essentially a storage device
for your logs. Each `winston` logger can have multiple transports (see:
[Transports]) configured at different levels (see: [Logging levels]). For
example, one may want error logs to be stored in a persistent remote location
(like a database), but all logs output to the console or a local file.

`winston` aims to decouple parts of the logging process to make it more
flexible and extensible. Attention is given to supporting flexibility in log
formatting (see: [Formats]) & levels (see: [Using custom logging levels]), and
ensuring those APIs decoupled from the implementation of transport logging
(i.e. how the logs are stored / indexed, see: [Adding Custom Transports]) to
the API that they exposed to the programmer.

## Quick Start

TL;DR? Check out the [quick start example][quick-example] in `./examples/`.
There are a number of other examples in [`./examples/*.js`][examples].
Don't see an example you think should be there? Submit a pull request
to add it!

## Usage

The recommended way to use `winston` is to create your own logger. The
simplest way to do this is using `winston.createLogger`:

``` js
const winston = require('winston');

const logger = winston.createLogger({
  level: 'info',
  format: winston.format.json(),
  defaultMeta: { service: 'user-service' },
  transports: [
    //
    // - Write all logs with importance level of `error` or higher to `error.log`
    //   (i.e., error, fatal, but not other levels)
    //
    new winston.transports.File({ filename: 'error.log', level: 'error' }),
    //
    // - Write all logs with importance level of `info` or higher to `combined.log`
    //   (i.e., fatal, error, warn, and info, but not trace)
    //
    new winston.transports.File({ filename: 'combined.log' }),
  ],
});

//
// If we're not in production then log to the `console` with the format:
// `${info.level}: ${info.message}