udisks.js

function checkUsbDrive() {
	var STORAGED_SERVICE = "org.freedesktop.UDisks2";
	var STORAGED_OPATH_PFX = "/org/freedesktop/UDisks2";
	var STORAGED_IFACE_PFX = "org.freedesktop.UDisks2";

	var udisks = cockpit.dbus(STORAGED_SERVICE);
	var udisks_manager = udisks.proxy(STORAGED_IFACE_PFX,
									STORAGED_OPATH_PFX + "/Manager", { watch: true });
	udisks_manager.wait();
	console.log(udisks_manager.valid);
}