How can I add timestamp to logs using Node.js library Winston?

Question

I want to add timestamp to logs. What is the best way to achieve this?

Answer 1

I took Biswadev's answer and created a stringified JSON object. This way if i need to process the logs later it will be in a well structured format.

const winston = require('winston');
const { createLogger, format, transports } = require('winston');

const dotenv = require('dotenv');
dotenv.config();

var logger = createLogger({
    level: 'info',
    format: format.combine(
        format.timestamp({
            format: 'YYYY-MM-DD HH:mm:ss',
        }),
        format.printf((info) =>
            JSON.stringify({
                t: info.timestamp,
                l: info.level,
                m: info.message,
                s: info.splat !== undefined ? `${info.splat}` : '',
            }) + ','
        )
    ),
});

if (process.env.NODE_ENV !== 'PRODUCTION') {
    logger.add(new transports.Console({ format: winston.format.cli() }));

    // Turn these on to create logs as if it were production
    // logger.add(new transports.File({ filename: 'log/output/error.log', level: 'error' }));
    // logger.add(new transports.File({ filename: 'log/output/warn.log', level: 'warn' }));
    // logger.add(new transports.File({ filename: 'log/output/info.log', level: 'info' }));
} else {
    logger.add(new transports.File({ filename: 'log/output/error.log', level: 'error' }));
    logger.add(new transports.File({ filename: 'log/output/warn.log', level: 'warn' }));
    logger.add(new transports.File({ filename: 'log/output/info.log', level: 'info' }));
}

module.exports = {
    logger,
};

Usage:

app.listen(port, () => logger.info(`app is running on port ${port}`));

Output:

info.log file:

{"t":"2020-08-06 08:02:05","l":"info","m":"app is running on port 3001","s":""},

Console:

info:    app is running on port 3001