[](https://travis-ci.org/anigenero/log4js2)
log4js2 came about because of the lack of logging frameworks that did anything beyond a simple
console.log. This library is designed to mirror Apache Log4j 2 functionality (to the best
ability that a JavaScript framework can), while remaining fast, lightweight (~14KB compressed),
and void of any external dependencies. It can also serve as a drop-in replacement for log4js,
since the namespace and functions are mostly similar.
If you're building from source, simply run
npm install && npm run build
Or, you can install log4js2 from either bower or npm.
bower install log4js2 --save
npm install log4js2 --save
Simply require the log4js2 module.
var log4js = require('log4js2');
Or, for HTML implementations, place the log4js distribution in your HTML <head> tag.
<script type="text/javascript" src="dist/log4js2.es5.min.js"></script>
Then, log some stuff!!
// create the logger
var log = log4js.getLogger('myLogger');
// log an event
log.info('This is a log');
// output: "03-24-2016 12:00:18,670|myLogger:anonymous:3|This is a log"
Configure log4js using the configure() method. This must be the first thing you do. Otherwise, the first log you commit will not allow updates from this function
log4js.configure({
layout : '%d{DEFAULT} [%level] %logger %M:%line - %message',
appenders : [ 'consoleAppender' ],
loggers : [ {
logLevel : log4js.LogLevel.INFO
} ],
allowAppenderInjection : true
});
Type: Boolean
Default: false
Turn on or off the ability to inject appenders. If set to false, no appenders can be added after the first log. This may be useful if you need to add an appender during runtime.
Type: Array.<String>
Default: [ 'consoleAppender' ]
Sets the appenders for the given log configuration. Packaged with log4js2 is the console appender . You can develop your own appenders to add more functionality.
Type: Array.<Object>
Default: [{ tag : 'main', logLevel : log4js.LogLevel.INFO }]
Sets the loggers for log4js2. The tag property specifies what logger the appender pertains to
(see below), and the logLevel specifies the logging level (use log4js.LogLevel). You can also
set a logger-specific layout using the layout property.
log4js.configure({
// ...
loggers : [ {
logLevel : log4js.LogLevel.INFO
}, {
tag : 'debugLogger',
logLevel : log4js.LogLevel.DEBUG
} ]
});
var log = log4js.getLogger('myLogger');
var debugLog = log4js.getLogger('debugLogger');
log.debug('This message will not show');
debugLog.debug('This message will show');
Type: String
Default: "%d [%p] %c - %m"
Sets the tagging layout for the logs. Refer to Apache's Log4j2 documentation for how to set the tag layout. Keep in mind that some of the layout tags are relatively more expensive, and should only really be used in a development environment - such as %method and %line. There are also a few layouts that are not yet implemented with log4js2:
log4js.configure({
layout : '%d{MM-dd-yyyy HH:mm:ss,S} [%level] %logger.%M:%line - %message',
// ...
});
var log = log4js.getLogger('myLogger');
log.warn('This is a log {}', 'with parameters');
// output: 03-24-2016 16:04:41,440 [WARN] myLogger.anonymous:15 - This is a log with parameters
In order to make the %method tag word, you must call from named function, like so:
function callerFunction() {
log.info('This is within a name function');
}
// output: 03-24-2016 16:17:50,360 [INFO] myLogger.callerFunction:3 - This is within a name function
Otherwise, non-named functions will simply display an 'anonymous' placeholder:
var callerFunction = function () {
log.info('This is an anonymous function');
};
// outputs: 03-24-2016 16:19:42,373 [INFO] myLogger.anonymous:3 - This is an anonymous function
You can output logs to a specific location or methodology using a custom appender. In ES6, you
just need to extend LogAppender. If you cannot utilize ES6, then simply create a function that
returns an object with the methods specified in the LogAppender class.
class MyAppender extends log4js.LogAppender {
static get name() {
return 'myappender';
}
append(logEvent) {
let result = this.format(logEvent);
// ... handle formatted result
}
// ... override methods
}
log4js.addAppender(MyAppender); // register the appender
appender LogAppender|function
Adds an appender to the log4js2 registry. This must be called before the first log, otherwise the
configuration option allowAppenderInjection must be set to true.
configuration Object
Sets the configuration. If no configuration is set before the first log, then the default configuration will be used. See configuration for options.
logger String [optional]
Gets a logger instance. If the logger is not set, the logger name will be pulled from the containing named instance it was created in (anonymous if unnamed).
logLevel Number (use log4js.LogLevel)
logger String [optional]
Sets the log level for a specific logger, or all loggers (if logger is not set).
FAQs
[](https://travis-ci.org/anigenero/log4js2) [](https://codecov.io/gh/anigenero/log4js2)
We found that log4js2 demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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