jquery和css3 如何實現航欄到底部上移（代碼）

.navigation {
    position: fixed;
    bottom: 100px;
    right: 100px;
    z-index: 100;
}.navigation {
    transition: bottom 2s;
    -webkit-transition: bottom 2s;
}

var nav = eval($('.navigation').offset().top - $(window).scrollTop());
$(window).on('scroll', function() {
    var navh = $('.navigation').height();
    var foot = parseInt($('.footer').offset().top - $(this).scrollTop() - navh);
    /*console.log(nav - foot);*/
    if(nav == foot || nav > foot) {
        $('.navigation').css({
            'position': 'fixed',
            'bottom': '400px'
        });
    } else {
        $('.navigation').css({
            'position': 'fixed',
            'bottom': '100px'
        });
    }
});