Get last and current quarter in javascript

function getQuarter(id) {
var d = new Date();
var quarter = Math.floor((d.getMonth() / 3));

switch (id) {
case "Current":
var firstDate = new Date(d.getFullYear(), quarter * 3, 1);
var endDate = new Date(firstDate.getFullYear(), firstDate.getMonth() + 3, 0);
break;
case "Previous":
var firstDate = new Date(d.getFullYear(), quarter * 3 - 3, 1);
var endDate = new Date(firstDate.getFullYear(), firstDate.getMonth() + 3, 0);
break;
}
}