iframeScrollPosition.js

// Use this script in the page that is hosting the iframe.
// It will send the scroll position of the parent frame to the iframe content window.
// Use `iframeScrollPosition.contentWindow.js` in the page contained within your iframe to receive the scroll position.
(function($) {
    $(document).ready(function () {
        var iframes = $("iframe");
        iframes.each(function (index, iframeElem) {
            var iframe = $(iframeElem);
            var sendScrollPosition = function () {
                var data = {
                    left: $(window).scrollLeft(),
                    top: $(window).scrollTop(),
                    offsetLeft: $(window).scrollLeft() - iframe.offset().left,
                    offsetTop: $(window).scrollTop() - iframe.offset().top
                };
                iframeElem.contentWindow.postMessage("parentScrollPosition:" + JSON.stringify(data), "*");
            };
            iframe.on('load', sendScrollPosition);
            $(window).scroll(sendScrollPosition);
        });
    });
})(jQuery);