Try to use :selected selector to grab the selected option elements,

$('#week option:selected').each(function(){
   //Your code to manipulate things over selected option elements
});

You can use length property of selected and total options, see below jquery :

var totalOptions = $('#week option').length; // all options available
var selectedOptions = $('#week option:selected').length;// selected options

if(totalOptions == selectedOptions)
 alert('All options selected');
else
 alert('Not all options selected');