Friendly Date Ranges (FreeCodeCamp)

friendly_date_range.js

function makeFriendlyDates(arr) {
  
	dateArr = [];
	
	months = {
	  '01':'January','02':'February','03':'March',
	  '04':'April','05':'May','06':'June',
	  '07':'July','08':'August','09':'September',
	  '10':'October','11':'November','12':'December'
	};
	
	function returnDay(day){
		var intDay = parseInt(day);
		if(intDay == 1 || intDay == 21 || intDay == 31){
			return intDay+"st";
		}
		else if (intDay == 2 || intDay == 22){
			return intDay+"nd";
		}
		else if(intDay == 3 || intDay == 23){
			return intDay+"rd";
		}
		else {
			return intDay+"th";
		}
	}
	
	var curYear = new Date().getFullYear();
	var monthFrom = months[arr[0].substr(5,2)];
	var monthTo = months[arr[1].substr(5,2)];
	var yearFrom = arr[0].substr(0,4);
	var yearTo = arr[1].substr(0,4);
	var dayFrom = returnDay(arr[0].substr(-2));
	var dayTo = returnDay(arr[1].substr(-2));
	var dateFrom = new Date(arr[0]);
	var dateTo = new Date(arr[1]);
	
	// 1 year = 31449600000
	var difference = dateTo.getTime() - dateFrom.getTime();
	
	if(difference <= 31449600000 && yearTo != curYear && yearTo != yearFrom && yearFrom != curYear){
		// console.log("within a year");
		dateArr.push(monthFrom + " " + dayFrom + ", " + yearFrom, monthTo + " " + dayTo);

	}
	
	else if(difference <= 31449600000 && yearTo != curYear && yearTo != yearFrom && yearFrom == curYear){
		// console.log("within a year");
		dateArr.push(monthFrom + " " + dayFrom, monthTo + " " + dayTo);

	}
	
	// if current year, same month 
	// eg: 2016-07-01 - 2016-07-04 ("July 1st", "4th")
	else if(curYear == yearFrom && monthFrom == monthTo){
		dateArr.push(monthFrom + " " + dayFrom, dayTo);
	}
	
	// if same year different months
	else if(yearFrom == yearTo && monthFrom != monthTo){
		dateArr.push(monthFrom + " " + dayFrom + ", " + yearFrom, monthTo + " " + dayTo);
	}
	
	// if same year, date and month
	else if (yearFrom == yearTo && monthFrom == monthTo && dayFrom == dayTo){
		dateArr.push(monthFrom + " " + dayFrom + ", " + yearFrom);
	}
	
	// push the rest. woop.
	else {
		dateArr.push(monthFrom + " " + dayFrom + ", " + yearFrom, monthTo + " " + dayTo + ", " + yearTo);
	}
	
return dateArr;
  
}