I need to save Firebug's or the Google Chrome Console panel's log. I tried console.log() to play with printing logs, but what I need is to programatically save these developer tools logs into files.
Firebug has an extension called ConsoleExport, which does exactly that. This extension exports the messages logged to Firebug's console in XML format. In the current released version 0.5b5 it only auto-exports to a server URL. Though, in the meantime code landed already (see issue 9) to auto-export to the file system, which will (hopefully) be released soon (see issue 21).