Node.js: Winston: Can I add default meta data to all log messages

Question

I'm using Winston in Node.js for logging. I know I can add metadata individually to each log message but is there a way to specify a default set of metadata that'll be added to every log message (such as the app name) as I don't want to specify it every time I need to send a log message.

Answer 1

For Winston v2 (see comments)

There are now rewriters.

For example, the below will add a property app to every metadata going through this logger.

    logger.rewriters.push(function(level, msg, meta) {       meta.app = 'myApp';       return meta;     }); 

You can also declare it when building the logger:

    new (winston.Logger)({             level: config.log[file].level,             rewriters: [                 (level, msg, meta) => {                     meta.app = 'myApp';                     return meta;                 }             ],             transports: [                 /*your transports*/             ]     }); 

Answer 2

For Winston v3:

const addAppNameFormat = winston.format(info => {   info.appName = "My Program";   return info; });  const logger = winston.createLogger({   format: winston.format.combine(     addAppNameFormat(),     winston.format.json()   ), transports: [new winston.transports.Console()] });  logger.warn('Danger Will Robinson!'); // {"message":"Danger Will Robinson!","level":"warn","appName":"My Program"} 

See: https://github.com/winstonjs/winston/blob/HEAD/UPGRADE-3.0.md#migrating-filters-and-rewriters-to-formats-in-winston3