Q: simple jQuery code for sticky navigation working in Chrome only? I'm using this code to create a clone of the navigation (#nav-wrap) that slides in upon user scroll. 
It works fine on Chrome but I just found out it doesn't in Firefox and IE10, I have no idea why though as no error is triggered, it just doesn't add the class 'down' to the body. Any idea why this could happen?
Here's the code:
JS
jQuery(document).ready(function($) {
    var $nav = $(".nav-wrap"),
        $clone = $nav.before($nav.clone().addClass("clone"));

    $(window).on("scroll", function() {
        var fromTop = $("body").scrollTop();
        $('body').toggleClass("down", (fromTop > 200));
    });
});

CSS
.nav-wrap {
    position: relative;
    height: 80px;
}

.nav-wrap.clone {
    position: fixed;
        top: -80px;
        right: 0;
        left: 0;
    transition: 0.2s top ease-in;
    z-index: 999;
}

body.down .nav-wrap.clone {
    top: 0; 
}

http://jsfiddle.net/XyVAG/193/
Thanks
