Lady, EVOLVED 
the for loop, but not the actual loop, just the for part
for (
let
dayInMonth = 1 - (new Date (year, month - 1, 1).getDay() + 6) % 7,
dayInWeek = 1,
week = calendarBody.insertRow(),
seasonIndex = +Object.entries(Array.from(seasons.values())).filter(( [ _, $ ] ) => month > $.startMonth || dayInMonth >= $.startDay).pop()[0],
nextSeason = Array.from(seasons.values())[(seasonIndex + 1) % seasons.size]
; daysInThisMonth >= dayInMonth || dayInWeek % 7 != 1
;
dayInMonth++,
dayInWeek = (dayInWeek + 1) % 7,
week = dayInWeek == 1 ? calendarBody.insertRow() : week,
!(nextSeason.startMonth > month || nextSeason.startDay > dayInMonth) ? (
seasonIndex = (seasonIndex + 1) % seasons.size,
nextSeason = Array.from(seasons.values())[(seasonIndex + 1) % seasons.size]
) : void null )
re: the for loop, but not the actual loop, just the for part
@Lady that sure is a way to write a loop
re: the for loop, but not the actual loop, just the for part
@aescling one might even say it is very loop-y
the javascript is horrid