The following will populate the window and document variables if they do not already exist. It should work from any scope/context:
if (typeof window === "undefined") {
//If there is no window defined, get the most recent.
var window = Components.classes["@mozilla.org/appshell/window-mediator;1"]
.getService(Components.interfaces.nsIWindowMediator)
.getMostRecentWindow("navigator:browser");
}
if (typeof document === "undefined") {
//If there is no document defined, get it
var document = window.content.document;
}
Here are some additional variables which might be useful to have available, depending on what you are doing:
if (typeof gBrowser === "undefined") {
//If there is no gBrowser defined, get it
var gBrowser = window.gBrowser;
}
var tab = gBrowser.selectedTab;
var browserForTab = gBrowser.getBrowserForTab( tab );
var notificationBox = gBrowser.getNotificationBox( browserForTab );
var ownerDocument = gBrowser.ownerDocument;