How to detect page zoom level in all modern browsers?

Question

1. How can I detect the page zoom level in all modern browsers? While this thread tells how to do it in IE7 and IE8, I can\'t find a good cross-browser solution.

Answer 1

This has worked great for me in webkit-based browsers (Chrome, Safari):

function isZoomed() {
    var width, mediaQuery;

    width = document.body.clientWidth;
    mediaQuery = '(max-width: ' + width + 'px) and (min-width: ' + width + 'px)';

    return !window.matchMedia(mediaQuery).matches;
}

Doesn't seem to work in Firefox though.

This also works in WebKit:

var zoomLevel = document.width / document.body.clientWidth;