<div class="progress">
  <div class="progress-bar progress-bar-striped" role="progressbar" style="width: 0" aria-valuenow="10" aria-valuemin="0" aria-valuemax="100"></div>
</div>

$(".progress-bar").each(function () {
  $(this).animate( {width: $(this).attr('aria-valuenow') + '%' }, 2000 );
});

$(window).scroll( function(){

  $(".progress-bar").each(function () {
    var bottom_of_object = $(this).position().top + $(this).outerHeight();
    var bottom_of_window = $(window).scrollTop() + $(window).height();
        if( bottom_of_window > bottom_of_object ){
            $(this).animate( {width: $(this).attr('aria-valuenow') + '%' }, 2000 );
        }
    });
});