get last day of month javascript

var lastday = function(y,m){
return  new Date(y, m +1, 0).getDate();
}
console.log(lastday(2014,0));
console.log(lastday(2014,1));
console.log(lastday(2014,11));

var today = new Date();
var lastDayOfMonth = new Date(today.getFullYear(), today.getMonth()+1, 0);