Create Log file in NodeJS

Question

How to create and save a log file in NodeJS for testing purpose?
The log file should contain the success/failure ratio of tests conducted.
I haven't tried anything yet as I am new to NodeJs.

Answer 1

Firstly do you know about npm?
If No, then read/research about it.
Else, then good. Look out for npm-modules suitable for logging task.
I shall recommend you winston-logger.

Install winston in your project as:

npm install winston --save

Here's a configuration ready to use out-of-box that I use frequently in my projects as logger.js under utils.

 /**
 * Configurations of logger.
 */
const winston = require('winston');
const winstonRotator = require('winston-daily-rotate-file');

const consoleConfig = [
  new winston.transports.Console({
    'colorize': true
  })
];

const createLogger = new winston.Logger({
  'transports': consoleConfig
});

const successLogger = createLogger;
successLogger.add(winstonRotator, {
  'name': 'access-file',
  'level': 'info',
  'filename': './logs/access.log',
  'json': false,
  'datePattern': 'yyyy-MM-dd-',
  'prepend': true
});

const errorLogger = createLogger;
errorLogger.add(winstonRotator, {
  'name': 'error-file',
  'level': 'error',
  'filename': './logs/error.log',
  'json': false,
  'datePattern': 'yyyy-MM-dd-',
  'prepend': true
});

module.exports = {
  'successlog': successLogger,
  'errorlog': errorLogger
};

And then simply import wherever required as this:

const errorLog = require('../util/logger').errorlog;
const successlog = require('../util/logger').successlog;

Then you can log the success as:

successlog.info(`Success Message and variables: ${variable}`);

and Errors as:

errorlog.error(`Error Message : ${error}`);

It also logs all the success-logs and error-logs in a file under logs directory date-wise as you can see here.

I have used "accesslog" instead of "successlog" as a keyword in my project.
And I didn't get what you meant about 'success/failure ratio'. In order to get the ratio simply count the no. of times success and error logs are logged.

Answer 2

require('mkdirp').sync('logs') // your log directory

var logger = require('log4js')

logger.configure({
    "appenders": [{
        "type": "console"
    }, {
        "type": "dateFile",
        "category": "log",
        "filename": "logs/exp",
        "pattern": "yyMMdd.log",
        "alwaysIncludePattern": true
    }],
    "replaceConsole": true
})

logger.info('success')
logger.error('fail')