jQuery to change values of progress-bar "aria-valuenow" attribute and CSS "width" property

$('#theprogressbar').attr('aria-valuenow', newprogress).css('width', newprogress);

value default is px if you want set % follow code below

$('#theprogressbar').attr('aria-valuenow', newprogress).css('width', newprogress+'%');

You could use

$('#theprogressbar').attr("aria-valuenow","the new value"); 
$('#theprogressbar').attr("style","width:"+theincrementingvalue); 

Or you could use .css in jquery http://api.jquery.com/css/

This works better:

var newprogress=80;
$('#id').width(newprogress + "%").attr('aria-valuenow', newprogress);