Jquery resize document height

HTML

<div class="stretch"></div>

CSS

.stretch {
    background-color: yellow;
    height: 50px;
    width: 50px;
}

JavaScript

function stretch() {
    var stretch_elem = $('.stretch');
    if (stretch_elem.length) {
        var h = $(document).height() - stretch_elem.offset().top - 370;
        stretch_elem.height(h);
    }
}

$(window).resize(stretch);