How can I make my Animate CC's 'Canvas' output react like background-size:cover?

!Thank you for your answer kglad but it doesn't help me because I don't want my animation to be responsive. I need that my canvas react exactly the same as a video or an image with background-size:cover. On mobile, the canvas is the same size but horizontally and vertically centered.

In CSS it would be this:

#animation_container { width: 100vw; height: 100vh;}

#canvas {

position: absolute;

top: 50%;

left: 50%;

transform: translate(-50%, -50%);

-webkit-transform: translate(-50%, -50%);

-ms-transform: translate(-50%, -50%);

min-height: 100%;

min-width: 100%;

}

But I have to generate it from Adobe Animate. So, for the moment, I have this script on the first frame of my animation but it doesn't work the way I need...

var page_body = document.getElementsByTagName("body")[0];

page_body.style.backgroundColor = "#00000";

page_body.style.overflow = "hidden";

page_body.style.position = "fixed";

var page_canvas = document.getElementsByTagName("canvas")[0];

stageWidth = page_canvas.width;

stageHeight = page_canvas.height;

var viewport = document.querySelector('meta[name=viewport]');

var viewportContent = 'width=device-width, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0, user-scalable=0';

if (viewport === null) {

var head = document.getElementsByTagName('head')[0];

viewport = document.createElement('meta');

viewport.setAttribute('name', 'viewport');

head.appendChild(viewport);

}

viewport.setAttribute('content', viewportContent);

function onResize() {

var widthToHeight = stageWidth / stageHeight;

var newWidth = window.innerWidth;

var newHeight = window.innerHeight;

var newWidthToHeight = newWidth / newHeight;

//

if (newWidthToHeight > widthToHeight) {

newWidth = newHeight * widthToHeight;

page_canvas.style.height = newHeight + "px";

page_canvas.style.width = newWidth + "px";

} else {

newHeight = newWidth / widthToHeight;

page_canvas.style.height = newHeight + "px";

page_canvas.style.width = newWidth + "px";

}

scale = newWidthToHeight / widthToHeight;

stage.width = newWidth;

stage.height = newHeight;

page_canvas.style.marginTop = ((window.innerHeight - newHeight) / 2) + "px";

page_canvas.style.marginLeft = ((window.innerWidth - newWidth) / 2) + "px";

}

window.onresize = function () {

onResize();

}

onResize();