Fake background-position cover with javascript by absolute positioning by an image inside its parent.

coverImage.js

/* Fake background-position cover with javascript by absolute positioning
 * an image inside its parent.
 */
function coverImage(image) {
    var $image = $(image);
    var $parent = $(image).parent();
    $parent.imagesLoaded(function () {
        var width = $image.width();
        var height = $image.height();

        var parent_width = $parent.outerWidth();
        var parent_height = $parent.outerHeight();

        var image_ratio = width/height;
        var parent_ratio = parent_width/parent_height;

        image.css({ position: 'absolute' });
        if (image_ratio > parent_ratio) {
            // Case: fit vertically and center horizontally
            image.css({
                height: parent_height,
                width: 'auto',
                top: 0
            });
            // recalculate since we change the height
            width = $image.width();
            image.css({
                left: parent_width/2 - width/2
            });
        } else {
            // Case: fit horizontally and center vertically
            image.css({
                height: 'auto',
                width: parent_width,
                top: 0
            });
            // recalculate since we change the height
            height = $image.height();
            image.css({
                top: parent_height/2 - height/2
            });
        }
    });
}