Dateの拡張

Date.prototype.js

Date.prototype.getMonthLength = function() {
  return this.getMonthLast().getDate();
}

Date.prototype.getPrevMonth = function() {
	return this.dateAdd("month", -1);
}


Date.prototype.getNextMonth = function() {
	return this.dateAdd("month", 1);
}


Date.prototype.getMonthFirst = function() {
	var tempDate = this.getDatePart();
	tempDate.setDate(1);
	return tempDate;
}


Date.prototype.getMonthLast = function() {
	var tempDate = this.getMonthFirst();
	tempDate.setMonth(tempDate.getMonth() + 1);
	tempDate.setDate(0);
	return tempDate;
}

Date.prototype.dateAdd = function(datePartName, spanCount) {
	var tempDate = new Date(this.getTime());
	var dateMemo;

	switch(datePartName) {
		case "year":
		case "y":
			tempDate = this.dateAdd("month", spanCount * 12);
			break;

		case "month":
		case "m":
			dateMemo = tempDate.getDate();
			tempDate.setDate(1);
			tempDate.setMonth(tempDate.getMonth() + spanCount + 1);
			tempDate.setDate(0);
			tempDate.setDate(Math.min(dateMemo, tempDate.getDate()));
			break;

		case "day":
		case "date":
		case "d":
			tempDate.setDate(tempDate.getDate() + spanCount);
			break;

		case "week":
			tempDate = this.dateAdd("day", spanCount * 7);
			break;

		case "hour":
			tempDate.setHours(tempDate.getHours() + spanCount);
			break;

		case "minute":
			tempDate.setMinutes(tempDate.getMinutes() + spanCount);
			break;

		case "second":
			tempDate.setSeconds(tempDate.getSeconds() + spanCount);
			break;

		case "millisecond":
			tempDate.setMilliseconds(tempDate.getMilliseconds() + spanCount);
			break;
	}

	return tempDate;
}


Date.prototype.dateDiff = function(datePartName, dateTarget) {
	var dateTemp;
	var ticksKijun = (new Date()).getDatePart().getTime();

	switch(datePartName) {
		case "year":
		case "y":
			return dateTarget.getFullYear() - this.getFullYear();

		case "month":
		case "m":
			return this.dateDiff("year", dateTarget) * 12 + dateTarget.getMonth() - this.getMonth();

		case "day":
		case "date":
		case "d":
			return Math.floor((dateTarget.getTime() - ticksKijun) / (1000*60*60*24)) - Math.floor((this.getTime() - ticksKijun) / (1000*60*60*24));

		case "week":
			dateTemp = this.getDatePart();
			dateTemp = dateTemp.dateAdd("day", -dateTemp.getDay());
			dateTarget = dateTarget.dateAdd("day", -dateTarget.getDay());
			return dateTemp.dateDiff("day", dateTarget) / 7;

		case "hour":
			return Math.floor((dateTarget.getTime() - ticksKijun) / (1000*60*60)) - Math.floor((this.getTime() - ticksKijun) / (1000*60*60));

		case "minute":
			return Math.floor((dateTarget.getTime() - ticksKijun) / (1000*60)) - Math.floor((this.getTime() - ticksKijun) / (1000*60));

		case "second":
			return Math.floor((dateTarget.getTime() - ticksKijun) / 1000) - Math.floor((this.getTime() - ticksKijun) / 1000);

		case "millisecond":
			return dateTarget.getTime() - this.getTime();
	}

	return null;
}


Date.prototype.toFormatString = function(format) {
	var week = new Array('日','月','火','水','木','金','土');

	var yyyy = this.getFullYear().toString();
	var yy = yyyy.slice(2);
	var M = (this.getMonth() + 1).toString();
	var MM = M.length == 1 ? "0" + M : M;
	var d = this.getDate().toString();
	var dd = d.length == 1 ? "0" + d : d;
	var ddd = week[this.getDay()];
	var H = this.getHours().toString();
	var HH = H.length == 1 ? "0" + H : H;
	var h = (this.getHours() % 12).toString();
	if(h == "0") {
		h = "12";
	}
	var hh = h.length == 1 ? "0" + h : h;
	var m = this.getMinutes().toString();
	var mm = m.length == 1 ? "0" + m : m;
	var s = this.getSeconds().toString();
	var ss = s.length == 1 ? "0" + s : s;
	var millis = '000' + this.getMilliseconds().toString();
	var f = millis.substr(millis.length - 3, 1);
	var ff = millis.substr(millis.length - 3, 2);
	var fff = millis.substr(millis.length - 3, 3);

	return format
		.replace(/yyyy/g, yyyy)
		.replace(/yy/g, yy)
		.replace(/MM/g, MM)
		.replace(/M/g, M)
		.replace(/ddd/g, ddd)
		.replace(/dd/g, dd)
		.replace(/d/g, d)
		.replace(/HH/g, HH)
		.replace(/H/g, H)
		.replace(/hh/g, hh)
		.replace(/h/g, h)
		.replace(/mm/g, mm)
		.replace(/m/g, m)
		.replace(/ss/g, ss)
		.replace(/s/g, s)
		.replace(/fff/g, fff)
		.replace(/ff/g, ff)
		.replace(/f/g, f);
}