i dont think the ds has a canvas element.
i tried doing snap legacy on the wii once. didnt work.
EDIT: the youtube video didnt embed for some reason. heres the link: https://www.youtube.com/watch?v=Q9MIyFaU2Cs
EDIT 2: i guess the 3ds DOES have a canvas element, based on a different post @coder_07 shared. guess theres just some unimplemented javascript function somewhere