How to get previous month name on given some month (in words not numerical value)?

Question

I want a function that gives the full name of prev month for any given month[not just current month] Ex: prevMonth(August) = July; prevMonth(January)= December.

I'm new to js and can't figure out how to use this array to get the result:

monthsarray: ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"]

Answer 1

Are expecting a simple solution like this?

var monthsarray = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"]

function prevMonth(curMonth) {

  var curMonthIndex = monthsarray.indexOf(curMonth);
  var prevMonthIndex;
  if (curMonthIndex == 0) prevMonthIndex = monthsarray.length - 1;
  else if (curMonthIndex == monthsarray.length - 1) prevMonthIndex = 0;
  else prevMonthIndex = curMonthIndex - 1;

  return monthsarray[prevMonthIndex];
}


console.log(prevMonth("August"));
console.log(prevMonth("December"));