Nuxt.js - How to add unix timestamp to logs using Winston.js library?

Question

I want to add unix timestamp to logs using Winston.

What is the best way to achieve this?

Thanks.

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

const logger = createLogger({
    format: format.combine(
        format.timestamp(), // ???
        format.json()
    ),
    transports: [
        new transports.Console(),
        new transports.File({filename: 'logs/error/error.log', level: 'error'}),
        new transports.File({filename: 'logs/activity/activity.log', level:'info'})
    ]
});