How to make canvas full width and height of viewport?

Question

css

How to make canvas area full width and height of viewport?
Demo - codepen.io/evg_/pen/xOpYvO
Tried to specify:

canvas.width = document.documentElement.clientWidth;
canvas.height = document.documentElement.clientHeight;

But when the screen is zoomed out, scrollbars appear. How can I make it so there are no scrollbars? So that the canvas can be said to be adaptive..

Answer 1

stack overflow