Why does adding filter to canavs elements,slows them down?

Question

In the following code, in class clouds I have added filter inside function new_pos if you remove that thing's work fine but with filter applied sometimes things slow down a lot ,why is it so?

Note:you won't see it mostly and it's rare but it happened three times with me after applying filter

https://code.sololearn.com/WZ18MUC04AVA/?ref=app

Answer 1

JaScript why not? If I Don't use it images will remain on the canvas ,I think it's better to clear them

Answer 2

I see no need for:
//cloud_inst.clear_clouds();

Answer 3

In your code the images overlapped but Abhay you can play of course it safe.