log

gistfile1.js

// this function works on firefox extension.

function log(){
    const Ci = Components.interfaces;
    const Cc = Components.classes;
    
    function firebug(method, args){
        var windowManager = Cc['@mozilla.org/appshell/window-mediator;1'].getService(Ci.nsIWindowMediator);
        var win =  windowManager.getMostRecentWindow("navigator:browser");
        if(win.FirebugConsole && win.FirebugContext) {
            var console = new win.FirebugConsole(win.FirebugContext, win.content);
            console[method].apply(console, args);
        } else if ( (win.Firebug || 0).Console ) {
            // Firebug 1.2~
            win.Firebug.Console.logFormatted.call(win.Firebug.Console, Array.slice(args), win.FirebugContext, method);
        } else {
            return false;
        }
        return true;
    }

    function lognative(){
        const ConsoleService = Cc["@mozilla.org/consoleservice;1"].getService(Ci.nsIConsoleService);
        ConsoleService.logStringMessage(arguments);
    }

    firebug('log',arguments) || lognative(arguments);
}