How to set log level in Winston/Node.js

If you are using the default logger, you can adjust the log levels like this:

const winston = require('winston');// ...winston.level = 'debug';

will set the log level to 'debug'. (Tested with winston 0.7.3, default logger is still around in 3.2.1).

However, the documentation recommends creating a new logger with the appropriate log levels and then using that logger:

const myLogger = winston.createLogger({  level: 'debug'});myLogger.debug('hello world');

If you are already using the default logger in your code base this may require you to replace all usages with this new logger that you are using:

const winston = require('winston');// default loggerwinston.log('debug', 'default logger being used');// custom loggermyLogger.log('debug', 'custom logger being used');

Looks like there is a level option in the options passed covered here

From that doc:

var logger = new (winston.Logger)({  transports: [    new (winston.transports.Console)({ level: 'error' }),    new (winston.transports.File)({ filename: 'somefile.log' })  ]});

Now, those examples show passing level in the option object to the console transport. When you use a file transport, I believe you would pass an options object that not only contains the filepath but also the level.

That should lead to something like:

var logger = new (winston.Logger)({  transports: [    new (winston.transports.File)({ filename: 'somefile.log', level: 'error' })  ]});

Per that doc, note also that as of 2.0, it exposes a setLevel method to change at runtime. Look in the Using Log Levels section of that doc.

There are 6 default levels in winston: silly=0(lowest), debug=1, verbose=2, info=3, warn=4, error=5(highest)

While creating the logger transports, you can specify the log level like:

new (winston.transports.File)({ filename: 'somefile.log', level: 'warn' })

Above code will set log level to warn, which means silly, verbose and info will not be output to somefile.log, while warn, debug and error will.

You can also define your own levels:

var myCustomLevels = {  levels: {    foo: 0,    bar: 1,    baz: 2,    foobar: 3  }};var customLevelLogger = new (winston.Logger)({ levels: myCustomLevels.levels });customLevelLogger.foobar('some foobar level-ed message');

Note that it's better to always include the 6 predefined levels in your own custom levels, in case somewhere used the predefined levels.