Node. js logging is an important part of supporting the complete application life cycle. From creation to debugging to planning new features, logs support us all the way. By analyzing the data in the logs, we can glean insights, resolve bugs much quicker, and detect problems early and as they happen.
Logging in Node. By default, it will not produce any output. To enable this logger, you have run your application with a special environment variable, called DEBUG . Once you do that, the debug module will come to life and will start producing log events for stdout.
Winston is a pretty good logging library. You can write logs out to a file using it.
Code would look something like:
var winston = require('winston');
var logger = new (winston.Logger)({
transports: [
new (winston.transports.Console)({ json: false, timestamp: true }),
new winston.transports.File({ filename: __dirname + '/debug.log', json: false })
],
exceptionHandlers: [
new (winston.transports.Console)({ json: false, timestamp: true }),
new winston.transports.File({ filename: __dirname + '/exceptions.log', json: false })
],
exitOnError: false
});
module.exports = logger;
You can then use this like:
var logger = require('./log');
logger.info('log to file');
I have looked through many loggers, and I wasn't able to find a lightweight solution - so I decided to make a simple solution that is posted on github.
I hope this helps you out.
http://bluejamesbond.github.io/Scribe.js/
https://github.com/bluejamesbond/Scribe.js
Log4js is one of the most popular logging library for nodejs application.
It supports many cool features:
Example:
Installation: npm install log4js
Configuration (./config/log4js.json
):
{"appenders": [
{
"type": "console",
"layout": {
"type": "pattern",
"pattern": "%m"
},
"category": "app"
},{
"category": "test-file-appender",
"type": "file",
"filename": "log_file.log",
"maxLogSize": 10240,
"backups": 3,
"layout": {
"type": "pattern",
"pattern": "%d{dd/MM hh:mm} %-5p %m"
}
}
],
"replaceConsole": true }
Usage:
var log4js = require( "log4js" );
log4js.configure( "./config/log4js.json" );
var logger = log4js.getLogger( "test-file-appender" );
// log4js.getLogger("app") will return logger that prints log to the console
logger.debug("Hello log4js");// store log in file
You can also use npmlog by issacs, recommended in https://npmjs.org/doc/coding-style.html.
You can find this module here https://github.com/isaacs/npmlog
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