function sort_days(days) {

To get today's day of week, use new Date().getDay(). This assumes Sunday = 0, Monday = 1, ..., Saturday = 6.

    var day_of_week = new Date().getDay();

To generate the list of the days of week, then slice the list of names:

    var list = [Sun,Mon,Tue,Wed,Thu,Fri,Sat];

    var sorted_list = list.slice(day_of_week).concat(list.slice(0,day_of_week));

(today is Friday, so sorted_list is ['Fri','Sat','Sun','Mon','Tue','Wed','Thu'])

Finally, to sort, use indexOf:

    return days.sort(function(a,b) { return sorted_list.indexOf(a) > sorted_list.indexOf(b); });

}

Putting it all together:

function sort_days(days) {

    var day_of_week = new Date().getDay();

    var list = [Sun,Mon,Tue,Wed,Thu,Fri,Sat];

    var sorted_list = list.slice(day_of_week).concat(list.slice(0,day_of_week));

    return days.sort(function(a,b) { return sorted_list.indexOf(a) > sorted_list.indexOf(b); });

}