Date.shortDays = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];  
  
function short_Days(dt)  
{   
   return Date.shortDays[dt.getDay()];  
}  
  
dt = new Date();  
console.log(short_Days(dt));  
  
dt = new Date(2015, 10, 1);  
console.log(short_Days(dt));