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The console service is the back-end for the Error Console, bundled with every Mozilla application, and for Firefox's Web Console and Browser Console. It is used to log various messages, warnings, and errors and to obtain the logged messages.
Inherits from: nsISupports Last changed in Gecko 19 (Firefox 19 / Thunderbird 19 / SeaMonkey 2.16)

Implemented by: @mozilla.org/consoleservice;1 as a service:

var consoleService = Components.classes["@mozilla.org/consoleservice;1"]
                     .getService(Components.interfaces.nsIConsoleService);

Method overview

void getMessageArray([array, size_is(count)] out nsIConsoleMessage messages, out uint32_t count);Obsolete since Gecko 19
void getMessageArray([optional] out uint32_t count, [retval, array, size_is(count)] out nsIConsoleMessage messages);
void logMessage(in nsIConsoleMessage message);
void logStringMessage(in wstring message);
void registerListener(in nsIConsoleListener listener);
void reset();
void unregisterListener(in nsIConsoleListener listener);

Methods

getMessageArray()

Get an array of all the messages logged so far.

Obsolete since Gecko 19 (Firefox 19 / Thunderbird 19 / SeaMonkey 2.16)
This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

void getMessageArray(
  [array, size_is(count)] out nsIConsoleMessage messages,
  out PRUint32 count
);
Parameters
messages
An array of current logged messages.
count
The number of messages in the array. If no messages are logged, this function will return a count of 0 but still will allocate one word for messages, so as to show up as a 0-length array when called from script.

void getMessageArray(
  [optional] out PRUint32 count,
  [retval, array, size_is(count)] out nsIConsoleMessage messages
);
Parameters
count
The number of messages in the array. If no messages are logged, this function will return a count of 0 but still will allocate one word for messages, so as to show up as a 0-length array when called from script.

Note: See the code samples below for how to call getMessageArray.

logMessage()

void logMessage(
  in nsIConsoleMessage message
);
Parameters
message
An nsIConsoleMessage to log.

logStringMessage()

Convenience method for logging simple messages.

void logStringMessage(
  in wstring message
);
Parameters
message
The string to log.

registerListener()

Registers a listener for notification when an error is logged.

Note: To guard against stack overflows from listeners that could log messages (it is easy to do this inadvertently from listeners implemented in JavaScript), we do not call any listeners when another error is already being logged.

void registerListener(
  in nsIConsoleListener listener
);
Parameters
listener
The nsIConsoleListener to add.

reset()

Clear the message buffer (For example, for privacy reasons).

void reset();
Parameters

None.

Note: Console listeners expect you to log an empty string message before calling reset so that they can clear their message buffers too. (This works before Gecko 1.9 too of course.)

unregisterListener()

Unregisters a listener.

void unregisterListener(
  in nsIConsoleListener listener
);
Parameters
listener
The nsIConsoleListener to remove.

Examples

Retrieving the message array

To retrieve the message array in Gecko prior to version 19:

function getConsoleMessageArray() {
  var consoleService = Components.classes["@mozilla.org/consoleservice;1"]
                                 .getService(Components.interfaces.nsIConsoleService);
  var array = {};
  consoleService.getMessageArray(array, {});
  return array.value;
}

To retrieve the message array in Gecko 19 or later:

function getConsoleMessageArray() {
  var consoleService = Components.classes["@mozilla.org/consoleservice;1"]
                                 .getService(Components.interfaces.nsIConsoleService);
  return consoleService.getMessageArray();
}

To retrieve the message array in a compatible way:

function getConsoleMessageArray() {
  var consoleService = Components.classes["@mozilla.org/consoleservice;1"]
                                 .getService(Components.interfaces.nsIConsoleService);
  var array = {};
  return consoleService.getMessageArray(array, {}) || array.value;
}

Logging a simple message

A common usage is to log a string message to console:

function LOG(msg) {
  var consoleService = Components.classes["@mozilla.org/consoleservice;1"]
                                 .getService(Components.interfaces.nsIConsoleService);
  consoleService.logStringMessage(msg);
}

Alternative logging methods include Components.utils.reportError and dump().

Logging a message with additional information

To include other information an nsIConsoleMessage object must be used. In this example nsIScriptError, which implements nsIConsoleMessage, is used to include information about the source file and line number of the error.

function myLogToConsole(aMessage, aSourceName, aSourceLine, aLineNumber, 
                        aColumnNumber, aFlags, aCategory)
{
  var consoleService = Components.classes["@mozilla.org/consoleservice;1"]
                                 .getService(Components.interfaces.nsIConsoleService);
  var scriptError = Components.classes["@mozilla.org/scripterror;1"]
                              .createInstance(Components.interfaces.nsIScriptError);
  scriptError.init(aMessage, aSourceName, aSourceLine, aLineNumber, 
                   aColumnNumber, aFlags, aCategory);
  consoleService.logMessage(scriptError);
}
  • aMessage — the string to be logged. You must provide this.
  • aSourceName — the URL of file with error. This will be a hyperlink in the Error Console, so you'd better use real URL. You may pass null if it's not applicable.
  • aSourceLine — the line #aLineNumber from aSourceName file. You are responsible for providing that line. You may pass null if you are lazy; that will prevent showing the source line in Error Console.
  • aLineNumber and aColumnNumber — specify the exact location of error. aColumnNumber is used to draw the arrow pointing to the problem character.
  • aFlags — one of flags declared in nsIScriptError. At the time of writing, possible values are:
    • nsIScriptError.errorFlag = 0
    • nsIScriptError.warningFlag = 1
    • nsIScriptError.exceptionFlag = 2 and
    • nsIScriptError.strictFlag = 4.
  • aCategory — a string indicating what kind of code caused the message. There are quite a few category strings and they do not seem to be listed in a single place. Hopefully, they will all be listed in nsIScriptError.idl eventually.

See also

 

Document Tags and Contributors

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 Contributors to this page: Naesten, Sheppy, Noitidart, Neil, madarche, trevorh, Philip Chee, Wjjohnst, Marcoos, Gomita, Fredchat, Ted_Mielczarek, Nickolay, Np, Callek
 Last updated by: Naesten,