jquery.progressBar.js

(function ($) {

    $.fn.progressBar = function(){
        return this.each(function() {
            var bar = this,
                bar_progress = $(bar).find('.loading');

            $(window).scroll(function(){
                if(scrolledIntoView(bar)){
                    var each_bar_width = bar_progress.attr('aria-valuenow');
                    bar_progress.width(each_bar_width + '%');
                };
            });
        });
    };

    function scrolledIntoView( element ) {
        var docViewTop = $(window).scrollTop(),
            docViewBottom = docViewTop + $(window).height(),
            elemTop = $(element).offset().top,
            elemBottom = elemTop + $(element).height();
        return ((elemBottom >= docViewTop) && (elemTop <= docViewBottom) && (elemBottom <= docViewBottom) && (elemTop >= docViewTop));
    };

}( jQuery ));