How do I change my node winston JSON output to be single line

Question

When I create a nodejs winston console logger and set json:true, it always output JSON logs in multiline format. If I pipe these to a file and try to grep that file, my grep hits only include part of the log line. I want winston to output my log lines in JSON format, but not to pretty print the JSON

Here is my config (coffeescript, apologies):

winston = require 'winston' logger = new (winston.Logger)(   transports: [     new winston.transports.Console({      json: true     })   ] ) 

And some sample output:

{   "name": "User4",   "level": "info",   "message": "multi line whyyyyy" } 

Answer 1

winston 3.x (current version)

Default formatter

const winston = require('winston'); const logger = winston.createLogger({   format: winston.format.json(),   transports: [     new winston.transports.Console()   ] }); 

Example

const test = { t: 'test', array: [1, 2, 3] }; logger.info('your message', test); // logger output: // {"t":"test","array":[1,2,3],"level":"info","message":"your message"} 

Custom formatter

const winston = require('winston');  const { splat, combine, timestamp, printf } = winston.format;  // meta param is ensured by splat() const myFormat = printf(({ timestamp, level, message, meta }) => {   return `${timestamp};${level};${message};${meta? JSON.stringify(meta) : ''}`; });  const logger = winston.createLogger({   format: combine(     timestamp(),     splat(),     myFormat   ),   transports: [     new winston.transports.Console()   ] }); 

Example:

const test = { t: 'test', array: [1, 2, 3] }; // NOTE: wrapping object name in `{...}` ensures that JSON.stringify will never  // return an empty string e.g. if `test = 0` you won't get any info if  // you pass `test` instead of `{ test }` to the logger.info(...) logger.info('your message', { test }); // logger output: // 2018-09-18T20:21:10.899Z;info;your message;{"test": {"t":"test","array":[1,2,3]}} 

winston 2.x (legacy version)

It seems that the accepted answer is outdated. Here is how to do this for current winston version (2.3.1):

var winston = require('winston'); var logger = new (winston.Logger)({   transports: [     new (winston.transports.Console)({      json: true,      stringify: (obj) => JSON.stringify(obj),     })   ] }) 

Note the parenthesis around winston.transports.Console.

Answer 2

The winston transports provide a way to override the stringify method, so by modifying the config above I got single line JSON output.

New config:

winston = require('winston') logger = new (winston.Logger)({   transports: [     new winston.transports.Console({      json: true,      stringify: (obj) => JSON.stringify(obj)     })   ] })