Does Defold Calculate Frames Per Second?

Questions
4

Hi,

Found this code to calculate Frames Per Second, but it won’t compile?:

	local last_time = os.clock()
	local os_dt_table = {}
	local os_dt_sum = 0
	local os_frames_per_second = 0
	local os_seconds_to_track = 2
	local os_expected_fps = 60

	local dt = os.clock() - last_time

	os_dt_sum = os_dt_sum + dt
	table.insert(os_dt_table, dt)
	local len = length(os_dt_table) -- <-- ERROR: attempt to call global 'length' (a nil value)?

	os_frames_per_second = len / os_dt_sum

	if len >= os_seconds_to_track*os_expected_fps then
		os_dt_sum = os_dt_sum - os_dt_table[1]
		splice(os_dt_table, 1, 1)
	end

	last_time = os.clock()

--	local n = gui.get_node("fps_os")
--	gui.set_text(n, "FPS (OS): " .. round(os_frames_per_second))

Any ideas on how to repair?
Thanks!

J.