write logs in file using log4js in node js

This solution helps u create logs folder and three files error.log,debug.log and info.log in ur folder log with the logs. Worked for me. Thanks.

var log4js = require('log4js'); // include log4js

log4js.configure({ // configure to use all types in different files.
    appenders: [
        {   type: 'file',
            filename: "/logs/error.log", // specify the path where u want logs folder error.log
            category: 'error',
            maxLogSize: 20480,
            backups: 10
        },
        {   type: "file",
            filename: "/logs/info.log", // specify the path where u want logs folder info.log
            category: 'info',
            maxLogSize: 20480,
            backups: 10
        },
        {   type: 'file',
            filename: "/logs/debug.log", // specify the path where u want logs folder debug.log
            category: 'debug',
            maxLogSize: 20480,
            backups: 10
        }
    ]
});

var loggerinfo = log4js.getLogger('info'); // initialize the var to use.
var loggererror = log4js.getLogger('error'); // initialize the var to use.
var loggerdebug = log4js.getLogger('debug'); // initialize the var to use.

loggerinfo.info('This is Information Logger');
loggererror.info('This is Error Logger');
loggerdebug.info('This is Debugger');

In the above code you are missing logger declaration : Add the line var logger = log4js.getLogger('cheese');

The whole block of code will be as follows:

var log4js = require('log4js');

log4js.loadAppender('file');
log4js.addAppender(log4js.appenders.file('logs/cheese.log'), 'cheese');

var logger = log4js.getLogger('cheese');

logger.setLevel('DEBUG');
logger.trace('Entering cheese testing');
logger.debug('Got cheese.');
logger.info('Cheese is Gouda.');
logger.warn('Cheese is quite smelly.');
logger.error('Cheese is too ripe!');
logger.fatal('Cheese was breeding ground for listeria.');

Reference

In version 2.x.

You'd need to do something like this:

var log4js = require('log4js');
log4js.configure({
  appenders: { 'file': { type: 'file', filename: 'logs/cheese.log' } },
  categories: { default: { appenders: ['file'], level: 'debug' } }
});

var logger = log4js.getLogger('cheese');

logger.setLevel('DEBUG');
logger.trace('Entering cheese testing');
logger.debug('Got cheese.');
logger.info('Cheese is Gouda.');
logger.warn('Cheese is quite smelly.');
logger.error('Cheese is too ripe!');
logger.fatal('Cheese was breeding ground for listeria.');

If you want to dynamically create files based on properties in the log message (like filename above), then take a look at the multiFile appender.

Log4js has a feature for multifile config. See here

log4js.configure({
  appenders: {
    out: { type: 'stdout' },
    afile: { type: 'multiFile', base: 'logs/', property: 'categoryName', extension: '.log' }
  },
  categories: {
    default: { appenders: ['out'], level: 'info' },
    tofile: { appenders: ['afile'], level: 'debug' }
  }
});

Then to start logging in a file logs/xyz.log:

const xyzlog = log4js.getLogger('tofile.xyz');
xyzlog.info('Hello!');