var month_name = function(dt){  
mlist = [ "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" ];  
  return mlist[dt.getMonth()];  
}  
console.log(month_name(new Date("10/11/2009")));  
console.log(month_name(new Date("11/13/2014")));