A flexible, extensible, and easy to use logging system for javascript
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SimplyLog is a project meant to bring flexible and controllable logging into javascript. The primary goals are extensibility, simplicity, and compatibility. This tool is intended to allow developers to quickly turn logging on and off as they are debugging a site. SimplyLog also provides a way to attach more than just a console appender which can be used to log to a remote server, a file, or whatever else comes up as a log container. As of now the only appender provided is the console but contributions for more appenders will gladly be accepted.


Creating a new logger

// Create a new console logger named example logger
//   A console logger is a logger with the console appender already
//   attached to it
var log = SimplyLog.consoleLogger('exampleLogger');

// Change the logging level from its default to TRACE level

// Send a message to the appender (which currently is a console appender)
log.trace('hello there', '!');
// The above line will result in the output exampleLogger:trace -> hello there!

// Changes this log to only output error messages

// This line won't actually output anything because the log level is set above it
log.debug('hello user');

Usage in Node

// Add the logger
var logger = require('simply-log');

var myLog = logger.consoleLogger('myLog');

Other Notes

SimplyLog keeps track of all loggers you create within it, this means you can reuse loggers in different parts of your app as long as SimplyLog is at the root. For instance

var logger = require('simply-log')


var doStuff = function() {
    // Do some stuff
    var myLog = logger.consoleLogger('stuffLogger');
    myLog.info("Info World");
    myLog.trace("Trace World");

var adjustLogging = function(level) {
    // Adjust the logger used in the 'doStuff' function


// Turn down logging to level of INFO, this will turn off the TRACE

Output from the above code chunk is, trace is turned off for our second call

stuffLogger:info -> Info World
stuffLogger:trace -> Trace World
stuffLogger:info -> Info World

API Crash Course

Logging a message

Messages are sent to the log appenders by calling the appropriate log level method. The method to call is always the level you want to send in all lower case. As of now the current levels are error, info, warn, debug, trace. Any number of arguments can be passed to these methods For instance the following is legal

SimplyLog.error('Lorem', 'ipsom', $(window));

Logging levels

SimplyLog currently supports the following logging levels in order of highest level to lowest level, setting the level a level down will also send all log levels above it to the appender.

  • SimplyLog.OFF Highest level, will disable all output
  • SimplyLog.ERROR Intended for error level logging
  • SimplyLog.INFO General information level
  • SimplyLog.WARN Display api level warnings
  • SimplyLog.DEBUG Display debug level messages
  • SimplyLog.TRACE Trace level, most verbose level of logging

Default level

You can setup SimplyLog to automatically set the logging level for all logs built by it by calling SimplyLog.setDefaultLevel(SimplyLog.{level});

Default Appenders

Adding a default appender will cause every log created after that point to also have that appender. You can add default appenders by calling the method

SimplyLog.addDefaultAppender(/*function(name, level, args) {}*/);

The arguments for the function you pass are

  • name - The name of the logger that is appending
  • level - The level of the message it is appending
  • args - All the args passed to the logging statement


Appenders are a way of allowing the log system to be extended, anything you can code can be called as an appender. Any number of appenders can be added to a logger to allow Tutorial and more complex appenders to come, to get started now take a look at the defaultConsoleAppender in simply-log.js, or take a look at the example below which is a copy of the defaultConsoleAppender but adds the timestamp.

var logFactory = require('simply-log');

logFactory.addDefaultAppender(function(name, level, args) {
        args.unshift(Date.now() + ' ' + name + ':' + level + ' ->');
        Function.prototype.apply.call(console.log, console, args);