create-node-mongo-express-app/bin/template/src/utils/winston.logger.ts

Node Js Template with MVC pattern, typescript, mongoose and express

import winston from 'winston';
// Define your severity levels.
const levels = {
  error: 0,
  warn: 1,
  info: 2,
  http: 3,
  debug: 4,
};

// This method set the current severity based on
// the current NODE_ENV: show all the log levels
// if the server was run in development mode; otherwise,
// if it was run in production, show only warn and error messages.
const level = () => {
  const env = process.env.NODE_ENV || 'development';
  const isDevelopment = env === 'development';
  return isDevelopment ? 'debug' : 'warn';
};

// Define different colors for each level.
// Colors make the log message more visible,
// adding the ability to focus or ignore messages.
const colors = {
  error: 'red',
  warn: 'yellow',
  info: 'blue',
  http: 'magenta',
  debug: 'white',
};

// Tell winston that you want to link the colors
// defined above to the severity levels.
winston.addColors(colors);

// Chose the aspect of your log customizing the log format.
const format = winston.format.combine(
  // Add the message timestamp with the preferred format
  winston.format.timestamp({ format: 'DD MMM, YYYY - HH:mm:ss:ms' }),
  // Tell Winston that the logs must be colored
  winston.format.colorize({ all: true }),
  // Define the format of the message showing the timestamp, the level and the message
  winston.format.printf(
    (info) => `[${info.timestamp}] ${info.level}: ${info.message}`,
  ),
);

// Define which transports the logger must use to print out messages.
// In this example, we are using three different transports
const transports = [
  // Allow the use the console to print the messages
  new winston.transports.Console(),
];

// Create the logger instance that has to be exported
// and used to log messages.
const logger = winston.createLogger({
  level: level(),
  levels,
  format,
  transports,
});

export default logger;