Jonathan Buchanan

Features

• Log messages at five levels of severity/granularity: DEBUG, INFO, WARN, ERROR and FATAL.
• Errors from window.onError are also logged.

• Logging level is configurable at run time.

Usage

Include suitable rules in your CSS to style log messages. See the example stylesheet above.

Initialise the logger with an output area, a level and true if you want to display controls to clear the log or change the logging level on the fly, false otherwise:

Logger.initialize("logger", Logger.INFO, false);

Sprinkle logging messages throughout your code while developing:

myFunction: function()
{
    Logger.debug(">>>myFunction");

    try
    {
        var aVar = this.doSomething();
        Logger.info(aVar);
    }
    catch(e)
    {
        Logger.error("Error doing something: " + e.message);
    }
    Logger.debug("<<<myFunction");
}

If you want to guard against creating log messages which are expensive or slow to create, use the is...Enabled() methods:

if (Logger.isInfoEnabled())
{
    Logger.info(this.assembleAHugeMessage());
}

Reap the rewards of being able to easily track the flow and state of your Javascript application.

Turn the Logger off for production:

Logger.initialize("logger", Logger.OFF, false);

Dependencies

• Prototype Framework

Reference

Property	Type	Description
DEBUG	Number	0: Code for the DEBUG level
INFO	Number	1: Code for the INFO level
WARN	Number	2: Code for the WARN level
ERROR	Number	3: Code for the ERROR level
FATAL	Number	4: Code for the FATAL level
OFF	Number	5: Code for the OFF level
levelNames	Array	Used to translate logging levels to their names for logging control
out	DOM Element	The Element logged messages will be added to
level	Number	The current logging level

Method	Kind	Argument	Description
initialize(out, level, showControls)	static	out the id of the element to log messages to - will be created if it does not exist level the lowest logging level which will be enabled showControls if true, logging controls will be shown	Logs the given message at a DEBUG level
debug(message)	static	message the message to be logged	Logs the given message at a DEBUG level
info(message)	static	message the message to be logged	Logs the given message at an INFO level
props(obj)	static	obj an object whose properties will be logged	Logs the properties of the given object at an INFO level
warn(message)	static	message the message to be logged	Logs the given message at a WARN level
error(message)	static	message the message to be logged	Logs the given message at a ERROR level
fatal(message)	static	message the message to be logged	Logs the given message at a FATAL level
isDebugEnabled()	static	(none)	Returns true if DEBUG level logging is enabled, false otherwise
isInfoEnabled()	static	(none)	Returns true if INFO level logging is enabled, false otherwise
isWarnEnabled()	static	(none)	Returns true if WARN level logging is enabled, false otherwise
isErrorEnabled()	static	(none)	Returns true if ERROR level logging is enabled, false otherwise
isFatalEnabled()	static	(none)	Returns true if FATAL level logging is enabled, false otherwise
_displayMessage(message, className, label)	static	message a log message className the class name to give the message which is output label a label for the log message	Outputs a log message
_getLogTime()	static	(none)	Returns the current time in HH:MM:SS.mmm format
_internal(message)	static	message the message to be logged	Logs the given message at an INTERNAL level
_logWindowError(message, url, line)	static	message an error message url the URL of a script in which an error occurred line the line number on which an error occurred	Bound to winow.onerror by initialize() to capture error events
_clearMessages()	static	(none)	Clears the message log
_setLevel(level)	static	level a logging level	Used to change the current logging level from the logging controls
_populateSelect(select, options)	static	select a DOM Element options a list of options with name and value properties	Used to populate the logging control select list
_removeChildNodes(node)	static	node a DOM Element from which to remove child nodes	Removes all child nodes from the given DOM Element