Get the first and last date of the previous month in JQuery

I have this script,

 var today = new Date();
 var dd = today.getDate();
 var ddd = today.getDate()-1;
 var dddd = today.getDate()-2;

 var mm = today.getMonth()+1; //January is 0!
 var yyyy = today.getFullYear();
 if(dd<10){
   dd='0'+dd
 } 
 if(mm<10){
   mm='0'+mm
 } 
 if(ddd<10){
   ddd='0'+ddd
 } 

 var today = dd+'/'+mm+'/'+yyyy;
 var d2 = ddd+'/'+mm+'/'+yyyy;
 var d3 = dddd+'/'+mm+'/'+yyyy;

With this i obtain the last 3 days of the current day but in this case today is 02 if i rest two days i obtain 0 but i want in this case the last day of the previous month, how can do this?

Here is my fiddle

Answer

That’s the first day of the current month new Date(now.getFullYear(), now.getMonth(), 1) to get the last day of the previous month create a date 1-day earlier: new Date(now.getFullYear(), now.getMonth(), 1 - 1).

To get the first day of the previous month we should substract 1 from the month component new Date(now.getFullYear(), now.getMonth() - 1, 1) but there is an issue if the current month is January (0) and the previous month is December (11). Hence I wrapped the month expression creating a cycle so it always returns a positiove value.

var now = new Date();
var prevMonthLastDate = new Date(now.getFullYear(), now.getMonth(), 0);
var prevMonthFirstDate = new Date(now.getFullYear() - (now.getMonth() > 0 ? 0 : 1), (now.getMonth() - 1 + 12) % 12, 1);

var formatDateComponent = function(dateComponent) {
  return (dateComponent < 10 ? '0' : '') + dateComponent;
};

var formatDate = function(date) {
  return formatDateComponent(date.getMonth() + 1) + '/' + formatDateComponent(date.getDate()) + '/' + date.getFullYear();
};

document.write(formatDate(prevMonthFirstDate) + ' - ' + formatDate(prevMonthLastDate));