offsetHeight, clientHeight and scrollHeight or offsetWidth, clientWidth and scrollWidth return wrong value for Mackbook retina display

Question

I am trying to get retina display document size through JavaScript code

var size = {
    width: Math.max(
        document.documentElement.clientWidth,
        document.body.scrollWidth,
        document.documentElement.scrollWidth,
        document.body.offsetWidth,
        document.documentElement.offsetWidth
    ),
    height: Math.max(
        document.documentElement.clientHeight,
        document.body.scrollHeight,
        document.documentElement.scrollHeight,
        document.body.offsetHeight,
        document.documentElement.offsetHeight
    )
};

but it will give only half image size in retina display, its working fine on other display any suggestion how to get clientWidth ,scrollWidth etc for retina display through javascript

Answer 1

Retina sets devicePixelRatio to 2 if you multiply your heights and widths by this parameter (which is in most cases 1), you get your proper value.