jquery extensions get's hidden layer height

getHiddenDimensions.js

//Optional parameter includeMargin is used when calculating outer dimensions
(function($) {
$.fn.getHiddenDimensions = function(includeMargin) {
    var $item = this,
        props = { position: 'absolute', visibility: 'hidden', display: 'block' },
        dim = { width:0, height:0, innerWidth: 0, innerHeight: 0,outerWidth: 0,outerHeight: 0 },
        $hiddenParents = $item.parents().andSelf().not(':visible'),
        includeMargin = (includeMargin == null)? false : includeMargin;

    var oldProps = [];
    $hiddenParents.each(function() {
        var old = {};

        for ( var name in props ) {
            old[ name ] = this.style[ name ];
            this.style[ name ] = props[ name ];
        }

        oldProps.push(old);
    });

    dim.width = $item.width();
    dim.outerWidth = $item.outerWidth(includeMargin);
    dim.innerWidth = $item.innerWidth();
    dim.height = $item.height();
    dim.innerHeight = $item.innerHeight();
    dim.outerHeight = $item.outerHeight(includeMargin);

    $hiddenParents.each(function(i) {
        var old = oldProps[i];
        for ( var name in props ) {
            this.style[ name ] = old[ name ];
        }
    });

    return dim;
}
}(jQuery));