Express logger module with Winston + Morgan

logger.js

import winston from 'winston';
import morgan from 'morgan';
import json from 'morgan-json';

/* WINSTON */
const filterLevel = level => winston.format(info => info.level === level ? info : undefined)();

const logger = winston.createLogger({
  levels: { error: 0, warn: 1, info: 2, debug: 3, http: 4 },
  transports: [
    new winston.transports.Console({
      level: 'debug',
      format: winston.format.printf(info => `[${info.level.toUpperCase()}] ${info.message}`),
    }),
    new winston.transports.File({
      filename: "logs/errors.log",
      level: "error",
      format: winston.format.combine(
        winston.format.timestamp(), // Add a timestamp
        winston.format.json() // Save in JSON format
      )
    }),
    new winston.transports.File({
      filename: "logs/http.log",
      level: 'http',
      format: filterLevel('http'),
    }),
  ],
});

export default logger;

/* MORGAN */
morgan.token('user-id', req => req.user || '-');

const format = json(':date[iso] :remote-addr :user-id :method :url :status :res[content-length] :response-time');
const stream = { write: message => logger.http(JSON.parse(message)) };
export const httpLogger = morgan(format, { stream });