Strange symbols in log with winston

Question

Initialization:

var winston = require('winston');
var logger = new (winston.Logger)({
    levels: {
        trace: 0,
        input: 1,
        verbose: 2,
        prompt: 3,
        debug: 4,
        info: 5,
        data: 6,
        help: 7,
        warn: 8,
        error: 9
    },
    colors: {
        trace: 'magenta',
        input: 'grey',
        verbose: 'cyan',
        prompt: 'grey',
        debug: 'blue',
        info: 'green',
        data: 'grey',
        help: 'cyan',
        warn: 'yellow',
        error: 'red'
    }
});

logger.add(winston.transports.Console, {
    level: 'error',
    prettyPrint: true,
    colorize: true,
    silent: false,
    timestamp: false,
    json: false
});

For example I call logger like this:

logger.info("isSandBox: " + isSandBox);

In my IDEA I see:

info: isSandBox: true

But when I've uploaded this script to Ubuntu server, I saw in the log:

^[[32minfo^[[39m: isSandBox: true

How can I fix it?

Answer 1

The codes you're seeing are color code escapes. They are only useful when logging to a terminal/console, as they get interpreted by the terminal to change the text color. If the logs end up in a file, the codes are stored as-is, and are not really useful.

You can check if the output if a terminal, and only enable colorisation when it is:

logger.add(winston.transports.Console, {
    level       : 'error',
    prettyPrint : true,
    colorize    : process.stdout.isTTY,
    silent      : false,
    timestamp   : false,
    json        : false
});

More info on the isTTY flag here.

Answer 2

In case you weren't able to solve this.. I was able to just now.

const { createLogger, format, transports } = require('winston');
const { combine, timestamp, label, colorize, printf } = format;

const myFormat = printf(info => {
  return `${info.timestamp} ${info.label} ${info.level}: ${info.message}`;
});

const logger = createLogger({
  format: combine(
    colorize(),
    label({ label: '[app-server]' }),
    timestamp(),
    myFormat
  ),
  transports: [new transports.Console()]
});

module.exports = logger;

The myFormat var is what allows it. None of the out of box formatters have the ability to translate the color code escapes.