nsIConsoleService

From MDC

Contents 1 Summary 2 Examples 2.1 Logging a simple message 2.2 Logging a message with additional information

[edit] Summary

The console service is the back-end part of the JavaScript Console tool, bundled with every Mozilla application. It is used to log various messages, warnings, and errors and to obtain the logged messages.

Interface definition: xpcom/base/nsIConsoleService.idl

Contract ID: @mozilla.org/consoleservice;1

This interface is not frozen and is likely to change in future (bug 228205).

[edit] Examples

[edit] 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().

[edit] Logging a message with additional information

To include other information such as source file and line number, more complex code must be used.

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 JavaScript 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 JavaScript 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 don't seem to be listed in a single place. Hopefully, they will all be listed in nsIScriptError.idl eventually.