NodeJS Winston Logger

logger.js

const winston = require("winston");
const winstonFmt = winston.format;

const TIMESTAMP_FMT = "YYYY-MM-DD HH:mm:ss";

const NANOS_IN_MILLI = BigInt(1e6);
const LOG_LEVEL = process.env.LOG_LEVEL || "warn";
const LOG_LEVELS = {
    levels: {
        error: 0,
        warn: 1,
        info: 2,
        debug: 3
    },
    colors: {
        error: "red",
        warn: "yellow",
        info: "reset",
        debug: "reset"
    }
};

function formatter(info) {
    return `[${info.timestamp}][${info.level.toUpperCase()}][${info.label.toUpperCase()}] ${info.message}`;
}

class Logger {
    constructor() {
        throw new Error("Don't instantiate directly, call getLogger()");
    }

    static getLogger(label) {
        return winston.createLogger({
            level: LOG_LEVEL,
            levels: LOG_LEVELS.levels,
            transports: new winston.transports.Console(),
            format: winston.format.combine(
                winstonFmt.label({ label: label.toString() }),
                winstonFmt.timestamp({ format: TIMESTAMP_FMT }),
                winstonFmt.splat(),
                winstonFmt.printf(formatter),
                winstonFmt.colorize({ all: true, colors: LOG_LEVELS.colors })
            )
        });
    }

    static middleware(logger) {
        return (req, res, next) => {
            const responseStartTime = process.hrtime.bigint();
            res.on("finish", () => {
                const responseFinishTime = (process.hrtime.bigint() - responseStartTime) / NANOS_IN_MILLI;
                logger.info(
                    "%s %s %s %d %s - %d ms",
                    req.headers["forwarded"] || req.headers["x-forwarded-for"] || req.connection.remoteAddress,
                    req.method,
                    req.originalUrl,
                    res.statusCode,
                    res.get("Content-Length") ? res.get("Content-Length") : "-",
                    `${responseFinishTime}`.slice(-1)
                );
            });
            next();
        };
    }
}

module.exports = Logger;