Fill Browser with a Small Canvas

gistfile1.js

var preserveAspectRatio = true;

function fillBrowser (canvas) {
    if (preserveAspectRatio) {
        var dWidth = window.innerWidth / canvas.width;
        var dHeight = window.innerHeight / canvas.height;
        var newWidth;
        var newHeight;

        if (dWidth < dHeight) {
            newWidth = dWidth * canvas.width;
            newHeight = dWidth * canvas.height;
        } else {
            newWidth = dHeight * canvas.width;
            newHeight = dHeight * canvas.height;
        }

        canvas.style.width = ~~newWidth + 'px';
        canvas.style.height = ~~newHeight + 'px';
    } else {
        canvas.style.width = window.innerWidth + 'px';
        canvas.style.height = window.innerHeight + 'px';
    }
}