Quick and dirty JavaScript Logging Shim

Logger.js

/*global require, define */
define(function (require) {
	"use strict";

	var slice = Array.prototype.slice;

	// Simple logging shim which allows log messages to be filtered and redirected to a logging solution
	// of your choice when debugging.
	var Logger = {
		
		DEBUG: 1,
		INFO: 2,
		WARN: 4,
		ERROR: 8,
		OFF: 99,

		// Handles incoming log messages.
		logFunc: null,
		
		// Current log level.
		level: null,

		debug: function () {
			if (this.logFunc && Logger.DEBUG >= this.level) {
				this.logFunc.apply(null, slice.call(arguments).splice(0, 0, Logger.INFO));
			}
		},

		info: function () {
			if (this.logFunc && Logger.INFO >= this.level) {
				this.logFunc.apply(null, [Logger.INFO].concat(slice.call(arguments)));
			}
		},
		
		warn: function () {
			if (this.logFunc && Logger.WARN >= this.level) {
				this.logFunc.apply(null, [Logger.WARN].concat(slice.call(arguments)));
			}
		},
		
		error: function () {
			if (this.logFunc && Logger.ERROR >= this.level) {
				this.logFunc.apply(null, [Logger.ERROR].concat(slice.call(arguments)));
			}
		}
	};

	// Returns a String which represents the supplied log level value.
	Logger.getLevelName = function(level) {
		switch (level) {
			case Logger.INFO:
				return "INFO";
			case Logger.DEBUG:
				return "DEBUG";
			case Logger.WARN:
				return "WARN";
			case Logger.ERROR:
				return "ERROR";
			default:
				return "";
		}
	};

	// Aliases.
	Logger.log = Logger.info;

	// Default configuration disables logging
	Logger.level = Logger.OFF;

	// Enables deubugging at the supplied level.
	Logger.activate = function(level) {
		// Check for the presence of a logger.
		if (!"console" in window) {
			return;
		}

		Logger.level = level || Logger.DEBUG;

		Logger.logFunc = function(msgLvl) {
			var hdlr = window.console.log;

			// Delegate through to custom error loggers if present.
			if (msgLvl === Logger.WARN && window.console.warn) {
				hdlr = window.console.warn;
			} else if (msgLvl == Logger.ERROR && window.console.error) {
				hdlr = window.console.error;
			}

			hdlr.apply(window.console, slice.call(arguments, [1]));
		};
	};

	return Logger;
});

logger_example.js

var Logger = require('logger');

// Activate, defaults to forwarding all log messages to `window.console`.
Logger.activate();

// Log a message, use in place of `console.log()`
Logger.log("Example message", { key: "value" });
// >> Example message > Object

// Restrict logging to a level.
Logger.level = Logger.WARN;

Logger.debug("A debug message");
Logger.warn("zOMG! o_O");
Logger.error("ARGH!! 0.0");
// >> zOMG! o_O
// >> ARGH!! 0.0

// Redirect the logger function, function should expect the message level (Number)
// followed by the remaining log arguments.
Logger.logFunc = function(msgLevel) {
	alert("[" + Logger.getLevelName(msgLevel) + "] " + arguments[1]);
}