log4javascript 1.4 manual

Contents

Introduction

Anyone who has done a reasonable amount of JavaScript development will be familiar with alert as a means of debugging. For a small script, it works fine. But for anything of greater complexity than, say, a rollover script its shortcomings become apparent. The most obvious problem is the endless clicking of 'OK'. Another problem is that for a page heavily reliant on events generated from user actions, alerts can actually alter the way the page behaves. One final problem is infinite loops: without alerts, the browser will notice that the script has messed up and will offer the user the chance to stop the script running. With an alert inside an infinite loop, you're forced to kill the browser.

At the other end of the scale there is Venkman, a full-on JavaScript debugger for Mozilla-based browsers such as Firefox. Here I have to confess that I simply have not put in the time to learn how to make it work well for me and I suspect I am not alone.

Nowadays, easily the best option for day-to-day JavaScript development is the brilliant Firebug, a Firefox plugin with built-in debugger, console, logging, and profiler. It's a seriously impressive tool but by its very nature as a Firefox plugin can only be used in one of the typical target browsers for mainstream web development.

log4javascript was originally written as a cross-browser tool to ease the pain of JavaScript debugging without the time investment required to use a debugger effectively. It requires only a JavaScript include and one line of code to initialize with default settings. Having for several years used log4j and its .NET port log4net, it was natural for me to base it on log4j.

log4javascript is by no means the only JavaScript logging framework out there. It is not even the only JavaScript implementation of log4j. It turns out the name log4javascript is used by another JavaScript logging framework, and that the name log4js is used by at least two other pieces of software; this version of log4javascript is unrelated to any of those.

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Note about the log4javascript object

All of log4javascript's instantiable classes are accessible via the log4javascript object, which acts as a namespace. Therefore references to all class names must be preceded with "log4javascript.". For example:

var popUpAppender = new log4javascript.PopUpAppender();

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Loggers, Appenders, Layouts and Levels

A logger in log4javascript is the object on which log calls are made. A logger may be assigned zero or more appenders. An appender is an object that actually does the logging: for example, a PopUpAppender logs messages to a pop-up console window while an AjaxAppender uses HTTP to send log messages back to the server. Each appender is assigned a layout, which is responsible for formatting log messages that are passed to an appender.

Every log message has a level. This is the severity of the message. Available levels are TRACE, DEBUG, INFO, WARN, ERROR and FATAL - these correspond to the logging methods trace, debug, info, warn, error and fatal of Logger. Levels are ordered as follows: TRACE < DEBUG < INFO < WARN < ERROR < FATAL. This means the FATAL is the most severe and TRACE the least. Also included are levels called ALL and OFF intended to enable or disable all logging respectively.

Both loggers and appenders also have threshold levels (by default, DEBUG for loggers and ALL for appenders). Setting a level to either a logger or an appender disables log messages of severity lower than that level. For instance, if a level of INFO is set on a logger then only log messages of severity INFO or greater will be logged, meaning DEBUG and TRACE messages will not be logged. If the same logger had two appenders, one of level DEBUG and one of level WARN then the first appender will still only log messages of INFO or greater while the second appender will only log messages of level WARN or greater.

This allows the developer fine control over which messages get logged where.

Configuring appenders

From version 1.4, configuring appenders is only possible via configuration methods. As the number of configuration options increases it becomes increasingly undesirable to use constructor parameters, so support for it has been dropped.

Example

NB. The Ajax side of this example relies on having server-side processing in place.

First, log4javascript is initialized, and a logger (actually the anonymous logger) is assigned to a variable called log:

<script type="text/javascript" src="log4javascript.js"></script>
<script type="text/javascript">
    //<![CDATA[
    var log = log4javascript.getLogger();

log does not yet have any appenders, so a call to log.debug() will do nothing as yet. For this example we will use a PopUpAppender for debugging purposes. Since the lifespan of the messages displayed in the pop-up is only going to be the same as that of the window, a PatternLayout is used that displays the time of the message and not the date (note that this is also true of PopUpAppender's default layout). The format of the string passed into PatternLayout is explained below.

    var popUpAppender = new log4javascript.PopUpAppender();
    var popUpLayout = new log4javascript.PatternLayout("%d{HH:mm:ss} %-5p - %m%n");
    popUpAppender.setLayout(popUpLayout);
    log.addAppender(popUpAppender);

Suppose that we also want to send log messages to the server, but limited to error messages only. To achieve this we use an AjaxAppender. Note that if no layout is specified then for convenience a default layout is used; in the case of AjaxAppender, that is HttpPostDataLayout, which formats log messages as a standard HTTP POST string from which a simple server-side script (not provided with log4javascript) will be able to extract posted parameters. This is fine for our purposes:

    var ajaxAppender = new log4javascript.AjaxAppender("myloggingservlet.do");
    ajaxAppender.setThreshold(log4javascript.Level.ERROR);
    log.addAppender(ajaxAppender);

Finally, some test log messages and the closing script tag:

    log.debug("Debugging message (appears in pop-up)");
    log.error("Error message (appears in pop-up and in server log)");
    //]]>
</script>

The full script:

<script type="text/javascript" src="log4javascript.js"></script>
<script type="text/javascript">
    //<![CDATA[
    var log = log4javascript.getLogger();
    var popUpAppender = new log4javascript.PopUpAppender();
    var popUpLayout = new log4javascript.PatternLayout("%d{HH:mm:ss} %-5p - %m%n");
    popUpAppender.setLayout(popUpLayout);
    log.addAppender(popUpAppender);
    var ajaxAppender = new log4javascript.AjaxAppender("myloggingservlet.do");
    ajaxAppender.setThreshold(log4javascript.Level.ERROR);
    log.addAppender(ajaxAppender);
    log.debug("Debugging message (appears in pop-up)");
    log.error("Error message (appears in pop-up and in server log)");
    //]]>
</script>

See this example in action (opens in new window)

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log4javascript static properties/methods

Properties

  • version
    The version number of your copy of log4javascript.
  • edition
    The edition of your copy of log4javascript.
  • logLog
    log4javascript's internal logging object. See below for more details.

Methods

  • getLogger
    Logger getLogger([String loggerName])
    Parameters:
    • loggerName [optional]

    Returns a logger with the specified name, creating it if a logger with that name does not already exist. If no name is specified, a logger is returned with name [anonymous], and subsequent calls to getLogger() (with no logger name specified) will return this same logger object.

    Note that the names [anonymous], [default], [null] and root are reserved for the anonymous logger, default logger, null logger and root logger respectively.

  • getDefaultLogger
    Logger getDefaultLogger()
    Convenience method that returns the default logger. The default logger has a single appender: a PopUpAppender with the default layout, width and height, and with focusPopUp set to false and lazyInit, useOldPopUp and complainAboutPopUpBlocking all set to true.
  • getNullLogger
    Logger getNullLogger()
    Returns an empty logger with no appenders. Useful for disabling all logging.
  • getRootLogger
    Logger getRootLogger()
    Returns the root logger from which all other loggers derive.
  • resetConfiguration
    void resetConfiguration()
    Resets the all loggers to their default level.
  • setEnabled
    void setEnabled(Boolean enabled)
    Parameters:
    • enabled
    Enables or disables all logging, depending on enabled.
  • isEnabled
    Boolean isEnabled()
    Returns true or false depending on whether logging is enabled.
  • addEventListener
    void addEventListener(String eventType, Function listener)
    Parameters:
    • eventType
    • listener

    Adds a function to be called when an event of the type specified occurs in log4javascript. Supported event types are load (occurs once the page has loaded) and error.

    Each listener is pased three paramaters:

    • sender. The object that raised the event (i.e. the log4javascript object);
    • eventType. The type of the event;
    • eventArgs. An object containing of event-specific arguments. For the error event, this is an object with properties message and exception. For the load event this is an empty object.
  • removeEventListener
    void removeEventListener(String eventType, Function listener)
    Parameters:
    • eventType
    • listener
    Removes the event listener function supplied for the event of the type specified.
  • dispatchEvent
    void dispatchEvent(String eventType, Object eventArgs)
    Parameters:
    • eventType
    • eventArgs
    Raises an event of type eventType on the log4javascript object. Each of the listeners for this type of event (registered via addEventListener) is called and passed eventArgs as the third parameter.
  • setEventTypes
    void setEventTypes(Array eventTypes)
    Parameters:
    • eventTypes
    Used internally to specify the types of events that the log4javascript object can raise.
  • setShowStackTraces
    void setShowStackTraces(Boolean show)
    Parameters:
    • show
    Enables or disables displaying of error stack traces, depending on show. By default, stack traces are not displayed. (Only works in Firefox)
  • evalInScope
    Object evalInScope(String expr)
    Parameters:
    • expr
    This evaluates the given expression in the log4javascript scope, thus allowing scripts to access internal log4javascript variables and functions. This was written for the purposes of automated testing but could be used by custom extensions to log4javascript.

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Levels

Levels are available as static properties of the log4javascript.Level object. In ascending order of severity:

  1. log4javascript.Level.ALL
  2. log4javascript.Level.TRACE
  3. log4javascript.Level.DEBUG
  4. log4javascript.Level.INFO
  5. log4javascript.Level.WARN
  6. log4javascript.Level.ERROR
  7. log4javascript.Level.FATAL
  8. log4javascript.Level.OFF

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Loggers

It is possible to have multiple loggers in log4javascript. For example, you may wish to have a logger for debugging purposes that logs messages to a pop-up window and a separate logger that reports any client-side application errors to the server via Ajax.

Logger hierarchy and appender additivity

From version 1.4, log4javascript has hierarchical loggers, implemented in the same way as log4j. In summary, you specify a logger's parent logger by means of a dot between the parent logger name and the child logger name. Therefore the logger tim.app.security inherits from tim.app, which in turn inherits from tim which, finally, inherits from the root logger.

What inheritance means for a logger is that in the absence of a threshold level set specifically on the logger it inherits its level from its parent; also, a logger inherits all its parent's appenders (this is known as appender additivity in log4j. This behaviour can be enabled or disabled via setAdditivity(). See below). In the above example, if the root logger has a level of DEBUG and one appender, each of the loggers tim.app.security, tim.app and tim would inherit the root level's appender. If, say, tim.app's threshold level was set to WARN, tim's effective level would remain at DEBUG (inherited from the root logger) while tim.app.security's effective level would be WARN, inherited from tim.app. The important thing to note is that appenders accumulate down the logger hierarchy while levels are simply inherited from the nearest ancestor with a threshold level set.

For a detailed explanation of the logger hierarchy, see the log4j manual.

Notes

  • It is not possible to instantiate loggers directly. Instead you must use one of the methods of the log4javascript object: getLogger, getRootLogger, getDefaultLogger or getNullLogger.

Logger methods

  • addAppender
    void addAppender(Appender appender)
    Parameters:
    • appender
    Adds the given appender.
  • removeAppender
    void removeAppender(Appender appender)
    Parameters:
    • appender
    Removes the given appender.
  • removeAllAppenders
    void removeAllAppenders()
    Clears all appenders for the current logger.
  • setLevel
    void setLevel(Level level)
    Parameters:
    • level
    Sets the level. Log messages of a lower level than level will not be logged. Default value is DEBUG.
  • getLevel
    Level getLevel()
    Returns the level explicitly set for this logger or null if none has been set.
  • getEffectiveLevel
    Level getEffectiveLevel()
    Returns the level at which the logger is operating. This is either the level explicitly set on the logger or, if no level has been set, the effective level of the logger's parent.
  • setAdditivity
    void setAdditivity(Boolean additivity)
    Parameters:
    • additivity

    Sets whether appender additivity is enabled (the default) or disabled. If set to false, this particular logger will not inherit any appenders form its ancestors. Any descendant of this logger, however, will inherit from its ancestors as normal, unless its own additivity is explicitly set to false.

    Default value is true.

  • getAdditivity
    Level getLevel()
    Returns whether additivity is enabled for this logger.
  • log
    void log(Level level, Object params)
    Parameters:
    • level
    • params
    Generic logging method used by wrapper methods such as debug, error etc.

    Notes

    • The signature of this method has changed in 1.4.
  • trace
    void trace(Object message1[, Object message2, ... ][, Error exception])
    Parameters:
    • message1[, message2...]
    • exception [optional]
    Logs one or more messages and optionally an error at level TRACE.

    Notes

    • Logging of multiple messages in one call is new in 1.4.
  • debug
    void debug(Object message1[, Object message2, ... ][, Error exception])
    Parameters:
    • message1[, message2...]
    • exception [optional]
    Logs one or more messages and optionally an error at level DEBUG.

    Notes

    • Logging of multiple messages in one call is new in 1.4.
  • info
    void info(Object message1[, Object message2, ... ][, Error exception])
    Parameters:
    • message1[, message2...]
    • exception [optional]
    Logs one or more messages and optionally an error at level INFO.

    Notes

    • Logging of multiple messages in one call is new in 1.4.
  • warn
    void warn(Object message1[, Object message2, ... ][, Error exception])
    Parameters:
    • message1[, message2...]
    • exception [optional]
    Logs one or more messages and optionally an error at level WARN.

    Notes

    • Logging of multiple messages in one call is new in 1.4.
  • error
    void error(Object message1[, Object message2, ... ][, Error exception])
    Parameters:
    • message1[, message2...]
    • exception [optional]
    Logs one or more messages and optionally an error at level ERROR.

    Notes

    • Logging of multiple messages in one call is new in 1.4.
  • fatal
    void fatal(Object message1[, Object message2, ... ][, Error exception])
    Parameters:
    • message1[, message2...]
    • exception [optional]
    Logs one or more messages and optionally an error at level FATAL.

    Notes

    • Logging of multiple messages in one call is new in 1.4.
  • isEnabledFor
    Boolean isEnabledFor(Level level, Error exception)
    Parameters:
    • level
    Returns whether the logger is enabled for the specified level.
  • isTraceEnabled
    Boolean isTraceEnabled()
    Returns whether the logger is enabled for TRACE messages.
  • isDebugEnabled
    Boolean isDebugEnabled()
    Returns whether the logger is enabled for DEBUG messages.
  • isInfoEnabled
    Boolean isInfoEnabled()
    Returns whether the logger is enabled for INFO messages.
  • isWarnEnabled
    Boolean isWarnEnabled()
    Returns whether the logger is enabled for WARN messages.
  • isErrorEnabled
    Boolean isErrorEnabled()
    Returns whether the logger is enabled for ERROR messages.
  • isFatalEnabled
    Boolean isFatalEnabled()
    Returns whether the logger is enabled for FATAL messages.
  • group
    void group(String name, Boolean initiallyExpanded)
    Parameters:
    • name
    • initiallyExpanded [optional]
    Starts a new group of log messages. In appenders that support grouping (currently PopUpAppender and InPageAppender), a group appears as an expandable section in the console, labelled with the name specified. Specifying initiallyExpanded determines whether the group starts off expanded (the default is true). Groups may be nested.
  • groupEnd
    void groupEnd()
    Ends the current group. If there is no group then this function has no effect.
  • time
    void time(String name, Level level)
    Parameters:
    • name
    • level [optional]
    Starts a timer with name name. When the timer is ended with a call to timeEnd using the same name, the amount of time that has elapsed in milliseconds since the timer was started is logged at level level. If not level is supplied, the level defaults to INFO.
  • timeEnd
    void timeEnd(String name)
    Parameters:
    • name
    Ends the timer with name name and logs the time elapsed.
  • assert
    void assert(Object expr)
    Parameters:
    • expr
    Asserts the given expression is true or evaluates to true. If so, nothing is logged. If not, an error is logged at the ERROR level.

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Appenders

Appender

There are methods common to all appenders, as listed below.

Methods

  • doAppend
    void doAppend(LoggingEvent loggingEvent)
    Parameters:
    • loggingEvent

    Checks the logging event's level is at least as severe as the appender's threshold and calls the appender's append method if so.

    This method should not in general be used directly or overridden.

  • append
    void append(LoggingEvent loggingEvent)
    Parameters:
    • loggingEvent
    Appender-specific method to append a log message. Every appender object should implement this method.
  • setLayout
    void setLayout(Layout layout)
    Parameters:
    • layout
    Sets the appender's layout.
  • getLayout
    Layout getLayout()
    Returns the appender's layout.
  • setThreshold
    void setThreshold(Level level)
    Parameters:
    • level
    Sets the appender's threshold. Log messages of level less severe than this threshold will not be logged.
  • getThreshold
    Level getThreshold()
    Returns the appender's threshold.
  • toString
    string toString()
    Returns a string representation of the appender. Every appender object should implement this method.

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AlertAppender

Editions: Standard

Displays a log message as a JavaScript alert.

Constructor

  • AlertAppender
    AlertAppender()

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AjaxAppender

Editions: Standard, Production

A flexible appender that asynchronously sends log messages to a server via HTTP.

The default configuration is to send each log message as a separate HTTP post request to the server using an HttpPostDataLayout, without waiting for a response before sending any subsequent requests. However, an AjaxAppender may be configured to do any one of or combinations of the following:

  • send log messages in batches (if the selected layout supports it - particularly suited to AjaxAppender are JsonLayout and XmlLayout, both of which allow batching);
  • wait for a response from a previous request before sending the next log message / batch of messages;
  • send all queued log messages at timed intervals.

Notes

  • AjaxAppender relies on the XMLHttpRequest object. It also requires the presence of correctly implemented setRequestHeader method on this object, which rules out Opera prior to version 8.01. If your browser does not support the necessary objects then one alert will display to explain why it doesn't work, after which the appender will silently switch off.
  • In AjaxAppender only, setLayout may not be called after the first message has been logged.
  • The default layout is HttpPostDataLayout.
  • From version 1.4, log message data is always sent as one or more name/value pairs. In the case of HttpPostDataLayout, data is sent the same as in previous versions. For other layouts such as JsonLayout and XmlLayout, the formatted log message is posted as the value of a parameter called data, though this may be changed via setPostVarName.

    From version 1.4.5, it is possible to override this behaviour so that logging data is sent as the request payload rather than as a posted form variable. This is done by setting the Content-Type header sent with each Ajax request explicitly. For example, if using a JsonLayout:

    ajaxApender.addHeader("Content-Type", "application/json");
  • From version 1.4, log message timestamps are sent as standard JavaScript times, i.e. the number of milliseconds since 00:00:00 UTC on January 1, 1970.
  • Also from version 1.4, any outstanding log messages may optionally be sent when the main page unloads (i.e. user follows a link, closes the window or refreshes the page). This behaviour may be enabled using setSendAllOnUnload; see below.

    This behaviour is dependent on window.onbeforeunload; unfortunately, Opera does not always raise this event, so this feature does not work reliably in Opera.

  • From version 1.4.8, AjaxAppender supports the sending of cookies in CORS requests via the new withCredentials constructor parameter.

Constructor

  • AjaxAppender
    AjaxAppender(String url[, Boolean withCredentials])
    Parameters:
    • url
      The URL to which log messages should be sent. Note that this is subject to the usual Ajax restrictions: the URL should be in the same domain as that of the page making the request.
    • withCredentials

      Since: 1.4.8

      Specifies whether cookies should be sent with each request.

Methods

  • setSendAllOnUnload
    void setSendAllOnUnload(Boolean sendAllOnUnload)

    [not available after first message logged]

    Whether to send all remaining unsent log messages to the server when the page unloads.

    Since version 1.4.3, the default value is false. Previously the default was true.

    Notes

    • This feature was found not to work prior to version 1.4.3 in WebKit browsers (e.g. Google Chrome, Safari). As a result, a workaround was implemented in 1.4.3 which has the unfortunate side effect of popping up a confirmation dialog to the user if there are any log messages to send when the page unloads. As a result, this feature is now obtrusive for the user and is therefore disabled by default.
    • This feature does not work in any version of Opera.
  • isSendAllOnUnload
    Boolean isSendAllOnUnload()
    Returns whether all remaining unsent log messages are sent to the server when the page unloads.
  • setPostVarName
    void setPostVarName(String postVarName)

    [not available after first message logged]

    Sets the post variable name whose value will the formatted log message(s) for each request.

    Default value is data.

    Notes

  • getPostVarName
    String getPostVarName()
    Returns the post variable name whose value will the formatted log message(s) for each request.
  • setTimed
    void setTimed(Boolean timed)

    [not available after first message logged]

    Whether to send log messages to the server at regular, timed intervals.

    Default value is false.

  • isTimed
    Boolean isTimed()
    Returns whether log messages are sent to the server at regular, timed intervals.
  • setWaitForResponse
    void setWaitForResponse(Boolean waitForResponse)

    [not available after first message logged]

    Sets whether to wait for a response from a previous HTTP request from this appender before sending the next log message / batch of messages.

    Default value is false.

  • isWaitForResponse
    Boolean isWaitForResponse()
    Returns whether the appender waits for a response from a previous HTTP request from this appender before sending the next log message / batch of messages.
  • setBatchSize
    void setBatchSize(Number batchSize)

    [not available after first message logged]

    Sets the number of log messages to send in each request. If not specified, defaults to 1.

    Notes

    • Setting this to a number greater than 1 means that the appender will wait until it has forwarded that many valid log messages before sending any more. This also means that if the page unloads for any reason and sendAllOnUnload is not set to true, any log messages waiting in the queue will not be sent.
    • If batching is used in conjunction with timed sending of log messages, messages will still be sent in batches of size batchSize, regardless of how many log messages are queued by the time the timed sending is invoked. Incomplete batches will not be sent except when the page unloads, if sendAllOnUnload is set to true.
  • getBatchSize
    Number getBatchSize()
    Returns the number of log messages sent in each request. See above for more details.
  • setTimerInterval
    void setTimerInterval(Number timerInterval)

    [not available after first message logged]

    Sets the length of time in milliseconds between each sending of queued log messages.

    Notes

    • timerInterval only has an effect in conjunction with timed (set by setTimed(). If timed is set to false then timerInterval has no effect.
    • Each time the queue of log messages or batches of messages is cleared, the countdown to the next sending only starts once the final request has been sent (and, if waitForResponse is set to true, the final response received). This means that the actual interval at which the queue of messages is cleared cannot be fixed.
  • getTimerInterval
    Number getTimerInterval()
    Returns the length of time in milliseconds between each sending of queued log messages. See above for more details.
  • setRequestSuccessCallback
    void setRequestSuccessCallback(Function requestSuccessCallback)

    Sets the function that is called whenever a successful request is made, called at the point at which the response is received. This feature can be used to confirm whether a request has been successful and act accordingly.

    A single parameter, xmlHttp, is passed to the callback function. This is the XMLHttpRequest object that performed the request.

  • setFailCallback
    void setFailCallback(Function failCallback)

    Sets the function that is called whenever any kind of failure occurs in the appender, including browser deficiencies or configuration errors (e.g. supplying a non-existent URL to the appender). This feature can be used to handle AjaxAppender-specific errors.

    A single parameter, message, is passed to the callback function. This is the error-specific message that caused the failure.

  • setSessionId
    void setSessionId(String sessionId)
    Sets the session id sent to the server each time a request is made.
  • getSessionId
    String getSessionId()
    Returns the session id sent to the server each time a request is made.
  • addHeader
    void addHeader(String name, String value)

    Adds an HTTP header that is sent with each request.

    Since: 1.4.3

    From 1.4.5, specifying the Content-Type header using this method will force logging data to be sent as the Ajax request payload rather than as a posted form field.

  • getHeaders
    Array getHeaders()
    Returns an array of the additional headers that are sent with each HTTP request. Each array item is an object with properties name and value.

    Since: 1.4.3

  • sendAll
    void sendAll()
    Sends all log messages in the queue. If log messages are batched then only completed batches are sent.

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PopUpAppender

Editions: Standard

Logs messages to a pop-up console window (note: you will need to disable pop-up blockers to use it). The pop-up displays a list of all log messages, and has the following features:

  • log messages are colour-coded by severity;
  • log messages are displayed in a monospace font to allow easy readability;
  • switchable wrap mode to allow wrapping of long lines
  • all whitespace in log messages is honoured (except in wrap mode);
  • filters to show and hide messages of a particular level;
  • search facility that allows searching of log messages as you type, with the following features:
    • supports regular expressions;
    • case sensitive or insensitive matching;
    • buttons to navigate through all the matches;
    • switch to highlight all matches;
    • switch to filter out all log messages that contain no matches;
    • switch to enable or disable the search;
    • search is dynamically applied to every log message as it is added to the console.
  • switch to toggle between logging from the top down and from the bottom up;
  • switch to turn automatic scrolling when a new message is logged on and off;
  • switch to turn off all logging to the pop-up (useful if a timer is generating unwanted log messages);
  • optional configurable limit to the number of log message that are displayed. If set and this limit is reached, each new log message will cause the oldest one to be discarded;
  • grouped log messages. Groups may be nested and each has a button to show or hide the log messages in that group;
  • clear button to allow user to delete all current log messages.
  • command prompt with up/down arrow history. Command line functions may be added to the appender. Several command line functions are built in:
    • $(String id)
      Prints a string representation of a single element with the id supplied.
    • dir(Object obj)
      Prints a list of a properties of the object supplied.
    • dirxml(HTMLElement el)
      Prints the XML source code of an HTML or XML element
    • cd(Object win)
      Changes the scope of execution of commands to the named frame or window (either a window/frame name or a reference to a window object may be supplied).
    • clear()
      Clears the console.
    • keys(Object obj)
      Prints a list of the names of all properties of the object supplied.
    • values(Object obj)
      Prints a list of the values of all properties of the object supplied.
    • expansionDepth(Number depth)
      Sets the number of levels of expansion of objects that are displayed by the command line. The default value is 1.

Notes

  • The default layout for this appender is PatternLayout with pattern string

    %d{HH:mm:ss} %-5p - %m{1}%n

Constructor

  • PopUpAppender
    PopUpAppender([Boolean lazyInit, Boolean initiallyMinimized, Boolean useDocumentWrite, Number width, Number height])
    Parameters:
    • lazyInit [optional]
      Set this to true to open the pop-up only when the first log message reaches the appender. Otherwise, the pop-up window opens as soon as the appender is created. If not specified, defaults to false.
    • initiallyMinimized [optional]

      Whether the console window should start off hidden / minimized. If not specified, defaults to false.

    • useDocumentWrite [optional]

      Specifies how the console window is created. By default, the console window is created dynamically using document's write method. This has the advantage of keeping all the code in one single JavaScript file. However, if your page sets document.domain then the browser prevents script access to a window unless it too has the same value set for document.domain. To get round this issue, you can set useDocumentWrite to false and log4javascript will instead use the external HTML file console.html (or console_uncompressed.html if you're using an uncompressed version of log4javascript.js), which must be placed in the same directory as your log4javascript.js file.

      Note that if useDocumentWrite is set to true, the old pop-up window will always be closed and a new one created whenever the page is refreshed, even if setUseOldPopUp(true) has been called.

      In general it's simpler to use the document.write method, so unless your page needs to set document.domain, useDocumentWrite should be set to true.

      If not specified, defaults to true.

    • width [optional]
      The outer width in pixels of the pop-up window. If not specified, defaults to 600.
    • height [optional]
      The outer height in pixels of the pop-up window. If not specified, defaults to 400.

Methods

  • isInitiallyMinimized
    Boolean isInitiallyMinimized()
    Returns whether the console window starts off hidden / minimized.
  • setInitiallyMinimized
    void setInitiallyMinimized(Boolean initiallyMinimized)
    [not available after initialization]
    Sets whether the console window should start off hidden / minimized.
  • isFocusPopUp
    Boolean isFocusPopUp()
    Returns whether the pop-up window is focussed (i.e. brought it to the front) when a new log message is added. Default value is false.
  • setFocusPopUp
    void setFocusPopUp(Boolean focusPopUp)
    Sets whether to focus the pop-up window (i.e. bring it to the front) when a new log message is added.
  • isUseOldPopUp
    Boolean isUseOldPopUp()

    Returns whether the same pop-up window is used if the main page is reloaded. If set to true, when the page is reloaded a line is drawn in the pop-up and subsequent log messages are added to the same pop-up. Otherwise, a new pop-up window is created that replaces the original pop-up. If not specified, defaults to true.

    Notes

    • In Internet Explorer 5, the browser prevents this from working properly, so a new pop-up window is always created when the main page reloads. Also, the original pop-up does not get closed.
  • setUseOldPopUp
    void setUseOldPopUp(Boolean useOldPopUp)
    [not available after initialization]
    Sets whether to use the same pop-up window if the main page is reloaded. See isUseOldPopUp above for details.
  • isComplainAboutPopUpBlocking
    Boolean isComplainAboutPopUpBlocking()
    Returns whether an alert is shown to the user when the pop-up window cannot be created as a result of a pop-up blocker. Default value is true.
  • setComplainAboutPopUpBlocking
    void setComplainAboutPopUpBlocking(Boolean complainAboutPopUpBlocking)
    [not available after initialization]
    Sets whether to announce to show an alert to the user when the pop-up window cannot be created as a result of a pop-up blocker.
  • isNewestMessageAtTop
    Boolean isNewestMessageAtTop()
    Returns whether new log messages are displayed at the top of the pop-up window. Default value is false (i.e. log messages are appended to the bottom of the window).
  • setNewestMessageAtTop
    void setNewestMessageAtTop(Boolean newestMessageAtTop)
    Sets whether to display new log messages at the top inside the pop-up window.
  • isScrollToLatestMessage
    Boolean isScrollToLatestMessage()
    Returns whether the pop-up window scrolls to display the latest log message when a new message is logged. Default value is true.
  • setScrollToLatestMessage
    void setScrollToLatestMessage(Boolean scrollToLatestMessage)
    Sets whether to scroll the pop-up window to display the latest log message when a new message is logged.
  • isReopenWhenClosed
    Boolean isReopenWhenClosed()
    Returns whether the pop-up window reopens automatically after being closed when a new log message is logged. Default value is false.
  • setReopenWhenClosed
    void setReopenWhenClosed(Boolean reopenWhenClosed)
    Sets whether to reopen the pop-up window automatically after being closed when a new log message is logged.
  • getWidth
    Number getWidth()
    Returns the outer width in pixels of the pop-up window.
  • setWidth
    void setWidth(Number width)
    [not available after initialization]
    Sets the outer width in pixels of the pop-up window.
  • getHeight
    Number getHeight()
    [not available after initialization]
    Returns the outer height in pixels of the pop-up window.
  • setHeight
    void setHeight(Number height)
    Sets the outer height in pixels of the pop-up window.
  • getMaxMessages
    Number getMaxMessages()
    Returns the largest number of log messages that are displayed and stored by the the console. Once reached, a new log message wil cause the oldest message to be discarded. Default value is null, which means no limit is applied.
  • setMaxMessages
    void setMaxMessages(Number maxMessages)
    [not available after initialization]
    Sets the largest number of messages displayed and stored by the console window. Set this to null to make this number unlimited.
  • isShowCommandLine
    Boolean isShowCommandLine()
    Returns whether the console includes a command line. Default value is true.
  • setShowCommandLine
    void setShowCommandLine(Boolean showCommandLine)
    Sets whether the console includes a command line.
  • getCommandLineObjectExpansionDepth
    Number getCommandLineObjectExpansionDepth()
    Returns the number of levels to expand when an object value is logged to the console. Each property of an object above this threshold will be expanded if it is itself an object or array, otherwise its string representation will be displayed. Default value is 1 (i.e. the properties of the object logged will be displayed in their string representation but not expanded).
  • setCommandLineObjectExpansionDepth:
    void setCommandLineObjectExpansionDepth(Number expansionDepth)
    Sets the number of levels to expand when an object value is logged to the console.
  • getCommandWindow
    Window getCommandWindow()
    Returns a reference to the window in which commands typed into the command line are currently being executed.
  • setCommandWindow
    void setCommandWindow(Window commandWindow)
    Sets the window in which commands typed into the command line are executed.
  • getCommandLayout
    Number getCommandLayout()
    Returns the layout used to format the output for commands typed into the command line. The default value is a PatternLayout with pattern string %m
  • setCommandLayout
    void setCommandLayout(Layout commandLayout)
    Sets the layout used to format the output for commands typed into the command line.
  • clear
    void clear()
    Clears all messages from the console window.
  • close
    void close()
    Closes the pop-up window.
  • show
    void show()
    Opens the pop-up window, if not already open.
  • hide
    void hide()
    Closes the pop-up window.
  • focus
    void focus()
    Brings the console window to the top and gives it the focus.
  • focusCommandLine
    void focusCommandLine()
    Brings the console window to the top and gives the focus to the command line.
  • focusSearch
    void focusSearch()
    Brings the console window to the top and gives the focus to the search box.
  • evalCommandAndAppend
    void evalCommandAndAppend(String expr)
    Evaluates the expression and appends the result to the console.
  • addCommandLineFunction
    void addCommandLineFunction(String functionName, Function commandLineFunction)

    Adds a function with the name specified to the list of functions available on the command line. This feature may be used to add custom functions to the command line.

    When you call the function on the command line, commandLineFunction is executed with the following three parameters:

    • appender. A reference to the appender in which the command was executed;
    • args. An array-like list of parameters passed into the function on the command line (actually a reference to the arguments object representing the parameters passed into the function by the user);
    • returnValue. This is an object with two properties that allow the function to control how the result is displayed:
      • appendResult. A boolean value that determines whether the returned value from this function is appended to the console. The default value is true;
      • isError. A boolean value that specifies whether the output of this function should be displayed as an error. The default value is false.

    The value returned by the function is formatted by the command layout and appended to the console.

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InPageAppender

Editions: Standard

Logs messages to a console window in the page. The console is identical to that used by the PopUpAppender, except for the absence of a 'Close' button.

Notes

  • Prior to log4javascript 1.3, InPageAppender was known as InlineAppender. For the sake of backwards compatibility, InlineAppender is still included in 1.3 and later as an alias for InPageAppender.
  • The default layout for this appender is PatternLayout with pattern string

    %d{HH:mm:ss} %-5p - %m{1}%n

Constructor

  • InPageAppender
    InPageAppender(HTMLElement container[, Boolean lazyInit, Boolean initiallyMinimized, Boolean useDocumentWrite, String width, String height])
    Parameters:
    • container
      The container element for the console window. This should be an HTML element.
    • lazyInit [optional]
      Set this to true to create the console only when the first log message reaches the appender. Otherwise, the console is initialized as soon as the appender is created. If not specified, defaults to true.
    • initiallyMinimized [optional]

      Whether the console window should start off hidden / minimized. If not specified, defaults to false.

      Notes

      • In Safari (and possibly other browsers) hiding an iframe resets its document, thus destroying the console window.
    • useDocumentWrite [optional]

      Specifies how the console window is created. By default, the console window is created dynamically using document's write method. This has the advantage of keeping all the code in one single JavaScript file. However, if your page sets document.domain then the browser prevents script access to a window unless it too has the same value set for document.domain. To get round this issue, you can set useDocumentWrite to false and log4javascript will instead use the external HTML file console.html (or console_uncompressed.html if you're using an uncompressed version of log4javascript.js), which must be placed in the same directory as your log4javascript.js file.

      In general it's simpler to use the document.write method, so unless your page needs to set document.domain, useDocumentWrite should be set to true.

      If not specified, defaults to true.

    • width [optional]
      The width of the console window. Any valid CSS length may be used. If not specified, defaults to 100%.
    • height [optional]
      The height of the console window. Any valid CSS length may be used. If not specified, defaults to 250px.

Methods

  • addCssProperty
    void addCssProperty(String name, String value)
    Sets a CSS style property on the HTML element containing the console iframe.
  • isVisible
    Boolean isVisible()
    Returns whether the console window is currently visible.
  • isInitiallyMinimized
    Boolean isInitiallyMinimized()
    Returns whether the console window starts off hidden / minimized.
  • setInitiallyMinimized
    void setInitiallyMinimized(Boolean initiallyMinimized)
    [not available after initialization]
    Sets whether the console window should start off hidden / minimized.
  • isNewestMessageAtTop
    Boolean isNewestMessageAtTop()
    Returns whether new log messages are displayed at the top of the console window.
  • setNewestMessageAtTop
    void setNewestMessageAtTop(Boolean newestMessageAtTop)
    Sets whether to display new log messages at the top inside the console window.
  • isScrollToLatestMessage
    Boolean isScrollToLatestMessage()
    Returns whether the pop-up window scrolls to display the latest log message when a new message is logged.
  • setScrollToLatestMessage
    void setScrollToLatestMessage(Boolean scrollToLatestMessage)
    Sets whether to scroll the console window to display the latest log message when a new message is logged.
  • getWidth
    String getWidth()
    Returns the outer width of the console window.
  • setWidth
    void setWidth(String width)
    [not available after initialization]
    Sets the outer width of the console window. Any valid CSS length may be used.
  • getHeight
    String getHeight()
    Returns the outer height of the console window.
  • setHeight
    void setHeight(String height)
    [not available after initialization]
    Sets the outer height of the console window. Any valid CSS length may be used.
  • getMaxMessages
    Number getMaxMessages()
    Returns the largest number of messages displayed and stored by the console window.
  • setMaxMessages
    void setMaxMessages(Number maxMessages)
    [not available after initialization]
    Sets the largest number of messages displayed and stored by the console window. Set this to null to make this number unlimited.
  • isShowCommandLine
    Boolean isShowCommandLine()
    Returns whether the console includes a command line. Default value is true.
  • setShowCommandLine
    void setShowCommandLine(Boolean showCommandLine)
    Sets whether the console includes a command line.
  • getCommandLineObjectExpansionDepth
    Number getCommandLineObjectExpansionDepth()
    Returns the number of levels to expand when an object value is logged to the console. Each property of an object above this threshold will be expanded if it is itself an object or array, otherwise its string representation will be displayed. Default value is 1 (i.e. the properties of the object logged will be displayed in their string representation but not expanded).
  • setCommandLineObjectExpansionDepth:
    void setCommandLineObjectExpansionDepth(Number expansionDepth)
    Sets the number of levels to expand when an object value is logged to the console.
  • getCommandWindow
    Window getCommandWindow()
    Returns a reference to the window in which commands typed into the command line are currently being executed.
  • setCommandWindow
    void setCommandWindow(Window commandWindow)
    Sets the window in which commands typed into the command line are executed.
  • getCommandLayout
    Number getCommandLayout()
    Returns the layout used to format the output for commands typed into the command line. The default value is a PatternLayout with pattern string %m
  • setCommandLayout
    void setCommandLayout(Layout commandLayout)
    Sets the layout used to format the output for commands typed into the command line.
  • clear
    void clear()
    Clears all messages from the console window.
  • show
    void show()

    Shows / unhides the console window.

    Notes

    • In Safari (and possibly other browsers), hiding an iframe resets its document, thus destroying the console window.
  • hide
    void hide()

    Hides / minimizes the console window.

    Notes

    • In Safari (and possibly other browsers), hiding an iframe resets its document, thus destroying the console window.
  • close
    void close()
    Removes the console window iframe from the main document.
  • focus
    void focus()
    Brings the console window to the top and gives it the focus.
  • focusCommandLine
    void focusCommandLine()
    Brings the console window to the top and gives the focus to the command line.
  • focusSearch
    void focusSearch()
    Brings the console window to the top and gives the focus to the search box.
  • evalCommandAndAppend
    void evalCommandAndAppend(String expr)
    Evaluates the expression and appends the result to the console.
  • addCommandLineFunction
    void addCommandLineFunction(String functionName, Function commandLineFunction)

    Adds a function with the name specified to the list of functions available on the command line. This feature may be used to add custom functions to the command line.

    When you call the function on the command line, commandLineFunction is executed with the following three parameters:

    • appender. A reference to the appender in which the command was executed;
    • args. An array-like list of parameters passed into the function on the command line (actually a reference to an arguments object);
    • returnValue. This is an object with two properties that allow the function to control how the result is displayed:
      • appendResult. A boolean value that determines whether the returned value from this function is appended to the console. The default value is true;
      • isError. A boolean value that specifies whether the output of this function should be displayed as an error. The default value is false.

    The value returned by the function is formatted by the command layout and appended to the console.

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BrowserConsoleAppender

Editions: Standardl

Writes log messages to the browser's built-in console, if present. This only works currently in Safari, Opera and Firefox with the excellent Firebug extension installed.

Notes

  • As of log4javascript 1.3, the default threshold for this appender is DEBUG as opposed to WARN as it was previously;
  • As of version 1.3, log4javascript has explicit support for Firebug's logging. This includes the following mapping of log4javascript's log levels onto Firebug's:

    • log4javascript TRACE, DEBUG -> Firebug debug
    • log4javascript INFO -> Firebug info
    • log4javascript WARN -> Firebug warn
    • log4javascript ERROR, FATAL -> Firebug error

    ... and the ability to pass objects into Firebug and take advantage of its object inspection. This is because the default layout is now NullLayout, which performs no formatting on an object.

Constructor

  • BrowserConsoleAppender
    BrowserConsoleAppender()

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Layouts

Layout

There are a few methods common to all layouts:

Methods

  • format
    String format(LoggingEvent loggingEvent)
    Parameters:
    • loggingEvent
    Formats the log message. You should override this method in your own layouts.
  • ignoresThrowable
    Boolean ignoresThrowable()
    Returns whether the layout ignores an error object in a logging event passed to its format method.
  • getContentType
    String getContentType()
    Returns the content type of the output of the layout.
  • allowBatching
    Boolean allowBatching()
    Returns whether the layout's output is suitable for batching. JsonLayout and XmlLayout are the only built-in layouts that return true for this method.
  • getDataValues
    Array getDataValues(LoggingEvent loggingEvent)
    Parameters:
    • loggingEvent
    Used internally by log4javascript in constructing formatted output for some layouts.
  • setKeys
    void setKeys(String loggerKey, String timeStampKey, String levelKey, String messageKey, String exceptionKey, String urlKey)
    Parameters:
    • loggerKey
      Parameter to use for the log message's logger name. Default is logger.
    • timeStampKey
      Parameter to use for the log message's timestamp. Default is timestamp.
    • levelKey
      Parameter to use for the log message's level. Default is level.
    • messageKey
      Parameter to use for the message itself. Default is message.
    • exceptionKey
      Parameter to use for the log message's error (exception). Default is exception.
    • urlKey
      Parameter to use for the current page URL. Default is url.
    This method is used to change the default keys used to create formatted name-value pairs for the properties of a log message, for layouts that do this. These layouts are JsonLayout and HttpPostDataLayout.
  • setCustomField
    void setCustomField(String name, String value)
    Parameters:
    • name
      Name of the custom property you wish to be included in the formmtted output.
    • value
      Value of the custom property you wish to be included in the formatted output.
    Some layouts (JsonLayout, HttpPostDataLayout, PatternLayout and XmlLayout) allow you to set custom fields (e.g. a session id to send to the server) to the formatted output. Use this method to set a custom field. If there is already a custom field with the specified name, its value will be updated with value.

    Notes

    • From version 1.4, the custom field value may be a function. In this case, the function is run at the time the layout's format method is called, with the following two parameters:

      • layout. A reference to the layout being used;
      • loggingEvent. A reference to the logging event being formatted.
  • hasCustomFields
    Boolean hasCustomFields()
    Returns whether the layout has any custom fields.

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NullLayout

Editions: All

The most basic layout. NullLayout's format() methods performs no formatting at all and simply returns the message logged.

Constructor

  • NullLayout
    NullLayout()

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SimpleLayout

Editions: Standard, Production

Provides basic formatting. SimpleLayout consists of the level of the log statement, followed by " - " and then the log message itself. For example,

DEBUG - Hello world

Constructor

  • SimpleLayout
    SimpleLayout()

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PatternLayout

Editions: All

Provides a flexible way of formatting a log message by means of a conversion pattern string. The behaviour of this layout is a full implementation of PatternLayout in log4j, with the exception of the set of conversion characters - log4javascript's is necessarily a subset of that of log4j with a few additions of its own, since many of the conversion characters in log4j only make sense in the context of Java.

The conversion pattern consists of literal text interspersed with special strings starting with a % symbol called conversion specifiers. A conversion specifier consists of the % symbol, a conversion character (possible characters are listed below) and format modifiers. For full documentation of the conversion pattern, see log4j's documentation. Below is a list of all conversion characters available in log4javascript.

Conversion characters

Conversion Character Effect
a

Outputs log messages specified as an array.

Behaves exactly like %m, except that multiple log messages are assumed to have been specified in the logging call as an array rather than as multiple parameters.

Since: 1.4

c

Outputs the logger name.

d

Outputs the date of the logging event. The date conversion specifier may be followed by a date format specifier enclosed between braces. For example, %d{HH:mm:ss,SSS} or %d{dd MMM yyyy HH:mm:ss,SSS}. If no date format specifier is given then ISO8601 format is assumed.

The date format specifier is the same as that used by Java's SimpleDateFormat. log4javascript includes a full implementation of SimpleDateFormat's format method, with the exception of the pattern letter 'z', (string representation of the timezone) for which the information is not available in JavaScript.

f

Outputs the value of a custom field set on the layout. If present, the specifier gives the index in the array of custom fields to use; otherwise, the first custom field in the array is used.

Since: 1.3

m

Outputs the log messages of the logging event (i.e. the log messages supplied by the client code).

As of version 1.4, multiple log messages may be supplied to logging calls. %m displays each log message (using the rules below) one after another, separated by spaces.

As of version 1.3, an object may be specified as the log message and will be expanded to show its properties in the output, provided that a specifier containing the number of levels to expand is provided. If no specifier is provided then the message will be treated as a string regardless of its type. For example, %m{1} will display an expansion of the object one level deep, i.e. each property of the object will be displayed but if the property value is itself an object it will not be expanded and will appear as [object Object].

n

Outputs a line separator.

p

Outputs the level of the logging event.

r

Outputs the number of milliseconds since log4javascript was initialized.

%

The sequence %% outputs a single percent sign.

Static properties

  • TTCC_CONVERSION_PATTERN
    Built-in conversion pattern, equivalent to %r %p %c - %m%n.
  • DEFAULT_CONVERSION_PATTERN
    Built-in conversion pattern, equivalent to %m%n.
  • ISO8601_DATEFORMAT
    Built-in date format (and also the default), equivalent to yyyy-MM-dd HH:mm:ss,SSS.
  • DATETIME_DATEFORMAT
    Built-in date format, equivalent to dd MMM YYYY HH:mm:ss,SSS.
  • ABSOLUTETIME_DATEFORMAT
    Built-in date format, equivalent to HH:mm:ss,SSS.

Constructor

  • PatternLayout
    PatternLayout(String pattern)
    Parameters:
    • pattern
      The conversion pattern string to use.

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XmlLayout

Editions: Standard, Production

Based on log4j's XmlLayout, this layout formats a log message as a fragment of XML. An example of the format of the fragment is as follows:

<log4javascript:event logger="[default]" timestamp="1201048234203" level="ERROR">
<log4javascript:message><![CDATA[Big problem!]]></log4javascript:message>
<log4javascript:exception><![CDATA[Nasty error on line number 1
    in file http://log4javascript.org/test.html]]></log4javascript:exception>
</log4javascript:event>

Notes

  • This layout supports batching of log messages when used in an AjaxAppender. A batch of messages is simply concatenated to form a string of several XML frgaments similar to that above.
  • The <log4javascript:exception> element is only present if an exception was passed into the original log call.
  • As of version 1.4, timestamps are returned as milliseconds since midnight of January 1, 1970 rather than seconds as in previous versions. This allows finer measurement of the time a logging event occurred and is also the JavaScript Date object's standard measurement.
  • Also as of version 1.4, multiple messages may be specified as separate parameters in a single logging call. In XmlLayout, multiple messages may be formatted as a single combined message or may be formated as several <log4javascript:message> elements inside one <log4javascript:messages> element as shown below:
    <log4javascript:event logger="[default]" timestamp="1201048234203" level="ERROR">
    <log4javascript:messages>
        <log4javascript:message><![CDATA[Big problem!]]></log4javascript:message>
        <log4javascript:message><![CDATA[Value of x when this error
            occurred: 3]]></log4javascript:message>
    </log4javascript:messages>
    <log4javascript:exception><![CDATA[Nasty error on line number 1
        in file http://log4javascript.org/test.html]]></log4javascript:exception>
    </log4javascript:event>
    
  • As of version 1.3, custom fields may be added to the output. Each field will add a tag of the following form inside the <log4javascript:event> tag:
    <log4javascript:customfield name="sessionid"><![CDATA[1234]]></log4javascript:customfield>
    

Constructor

  • XmlLayout
    XmlLayout([Boolean combineMessages])
    • combineMessages
      Whether or not to format multiple log messages as a combined single <log4javascript:message> element composed of each individual message separated by line breaks or to include a <log4javascript:message> element for each message inside one <log4javascript:messages> element. If not specified, defaults to true.

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JsonLayout

Editions: Standard, Production

Formats a logging event into JavaScript Object Notation (JSON). JSON is a subset of JavaScript's object literal syntax, meaning that log messages formatted with this layout can be interpreted directly by JavaScript and converted into objects. See json.org for more details about JSON.

Example:

{
    "logger": "[default]",
    "timeStamp": 1201048234203,
    "level": "ERROR",
    "url": "http://log4javascript.org/test.html",
    "message": "Big problem!",
    "exception": "Nasty error on line number 1 in file
        http://log4javascript.org/test.html"
}

The exception property is only present if an exception was passed into the original log call.

Notes

  • This layout supports batching of log messages when used in an AjaxAppender. When sent singly the layout formats the log message as a single JavaScript object literal; when sent as a batch, the messages are formatted as an array literal whose elements are log message objects.
  • As of version 1.3, custom fields may be added to the output. Each field will add a property of the following form to the main object literal:

        "sessionid": 1234
    
  • From version 1.4, the variable names used for log event properties such as the message, timestamp and exception are specified using the setKeys() method of Layout.
  • Also as of version 1.4, multiple messages may be specified as separate parameters in a single logging call. In JsonLayout, multiple messages may be formatted as a single combined message or may be formated as an array of messages as shown below:

    {
        "logger": "[default]",
        "timeStamp": 1201048234203,
        "level": "ERROR",
        "url": "http://log4javascript.org/test.html",
        "message": [
            "Big problem!",
            "Value of x when this error occurred: 3"
        ],
        "exception": "Nasty error on line number 1 in file
            http://log4javascript.org/test.html"
    }
    

Constructor

  • JsonLayout
    JsonLayout([Boolean readable, Boolean combineMessages])
    Parameters:
    • readable
      Whether or not to format each log message with line breaks and tabs. If not specified, defaults to false.
    • combineMessages
      Whether or not to format multiple log messages as a combined single message property composed of each individual message separated by line breaks or to format multiple messages as an array. If not specified, defaults to true.

Methods

  • isReadable
    Boolean isReadable()
    Returns whether or not to each log message is formatted with line breaks and tabs.

    Notes

    • setReadable has been removed in version 1.4. This property can be set via the constructor.

HttpPostDataLayout

Editions: Standard, Production

Formats the log message as a simple URL-encoded string from which a simple server-side script may extract parameters such as the log message, severity and timestamp. This is the default layout for AjaxAppender.

Constructor

  • HttpPostDataLayout
    HttpPostDataLayout()

Notes

  • As of version 1.3, custom fields may be added to the output. Each field will be added as a parameter to the post data.
  • From version 1.4, the variable names used for log event properties such as the message, timestamp and exception are specified using the setKeys() method of Layout.

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Enabling / disabling log4javascript

All logging can be enabled or disabled in log4javascript in a number of ways:

  • At any time, you can call log4javascript.setEnabled(enabled). This will enable or disable all logging, depending on whether enabled is set to true or false.
  • Assign a value to the global variable log4javascript_disabled. The idea of this is so that you can enable or disable logging for a whole site by including a JavaScript file in all your pages, and allowing this file to be included before log4javascript.js to guarantee that no logging can take place without having to alter log4javascript.js itself. Your included .js file would include a single line such as the following:

    var log4javascript_disabled = true;

  • Assign your logger object a value of log4javascript.getNullLogger().
  • Replace your copy of log4javascript_x.js with stubs/log4javascript_x.js, provided in the distribution. This file has a stub version of each of the functions and methods in the log4javascript API and can simply be dropped in in place of the main file. The compressed version of the stub is typically 15 times smaller than the compressed version of the main file.

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log4javascript error handling

log4javascript has a single rudimentary logger-like object of its own to handle messages generated by log4javascript itself. This logger is called LogLog and is accessed via log4javascript.logLog.

Methods

  • setQuietMode
    void setQuietMode(Boolean quietMode)
    Parameters:
    • quietMode
      Whether to turn quiet mode on or off.
    Sets whether LogLog is in quiet mode or not. In quiet mode, no messages sent to LogLog have any visible effect. By default, quiet mode is switched off.
  • setAlertAllErrors
    void setAlertAllErrors(Boolean alertAllErrors)
    Parameters:
    • showAllErrors
      Whether to show all errors or just the first.
    Sets how many errors LogLog will display alerts for. By default, only the first error encountered generates an alert to the user. If you turn all errors on by supplying true to this method then all errors will generate alerts.
  • debug
    void debug(String message[, Error exception])
    Parameters:
    • message
    • exception [optional]
    Logs a debugging message to an in-memory list. This implementation is new in version 1.4.
  • displayDebug
    void displayDebug()
    Displays an alert of all debugging messages. This method is new in version 1.4.
  • warn
    void warn(String message[, Error exception])
    Parameters:
    • message
    • exception [optional]
    Currently has no effect.
  • error
    void error(String message[, Error exception])
    Parameters:
    • message
    • exception [optional]
    Generates an alert to the user if and only if the error is the first one encountered and setAlertAllErrors(true) has not been called.

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Differences between log4javascript and log4j

For the sake of keeping log4javascript as light and useful as possible, many of the features of log4j that seem over-complex or inappropriate for JavaScript have not been implemented. These include:

  • Filters
  • Configurators
  • Renderers

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