十年前的js代码

这段js是12年写的，当时是为了在信息流中显示文章发表日期在几天前、几小时前、几分钟前这样的功能。

//将长整型的时间转化为距离现在的时间，刚刚，几分钟前，几小时前，几时几分，昨天几时几分，前天几时几分，
// 几月几日几时几分，年月日时分的形式
//参数 utcDate为想要转化的时间，为number类型，后台对应相应的长整型
function smartDateFormat(utcDate) {

	var crdate = new Date(utcDate);
	var cryear = crdate.getFullYear();
	var crmonth = crdate.getMonth() + 1;
	var crday = crdate.getDate();
	var crhour = crdate.getHours();
	var crminute = crdate.getMinutes();

	var currdate = new Date();
	var curryear = currdate.getFullYear();
	var currmonth = currdate.getMonth() + 1;
	var currday = currdate.getDate();
	var currhour = currdate.getHours();
	var currminute = currdate.getMinutes();

	if (crhour < 10) {
		crhour = "0" + crhour;
	}
	if (crminute < 10) {
		crminute = "0" + crminute;
	}
	if (currhour < 10) {
		currhour = "0" + currhour;
	}
	if (currminute < 10) {
		currminute = "0" + currminute;
	}

	if (cryear != curryear) {
		/* 年不同 */
		if (crmonth == 12 && currmonth == 1) {
			/* 月相邻 */
			var daydis = 31 - crday + currday;
			if (daydis == 1) {
				/* 相邻日 */
				var hourdis = 24 - crhour + currhour;//时差
				if (hourdis == 1) {
					/* 时相连 */
					var mindis = 60 - crminute + currminute;
					if (mindis > 60) {
						return hourdis + "小时前";
					} else {
						return mindis + "分钟前";
					}
				} else if (hourdis == 2) {
					return hourdis + "小时前";
				} else {
					return "昨天" + " " + crhour + ":" + crminute;
				}
			} else if (daydis == 2) {
				return "前天" + " " + crhour + ":" + crminute;;
			} else {
				return cryear + "年" + crmonth + "月" + crday + "日" + " " + crhour + ":" + crminute;
			}
		} else {
			/* 月不相邻 */
			return cryear + "年" + crmonth + "月" + crday + "日" + " " + crhour + ":" + crminute;
		}
	} else {
		/* 年相同 */
		if (crmonth != currmonth) {
			/* 月不同 */
			if (crmonth - currmonth == 1) {
				/* 月相邻 */
				var currdaycount = getDayOfMonth(cryear, crmonth);
				var daydis = currdaycount - crday + currday;
				if (daydis == 1) {
					/* 相邻日 */
					var hourdis = 24 - crhour + currhour;//时差
					if (hourdis == 1) {
						/* 时相连 */
						var mindis = 60 - crminute + currminute;
						if (mindis > 60) {
							return hourdis + "小时前";
						} else {
							return mindis + "分钟前";
						}
					} else if (hourdis == 2) {
						return hourdis + "小时前";
					} else {
						return "昨天" + " " + crhour + ":" + crminute;
					}
				} else if (daydis == 2) {
					return "前天" + " " + crhour + ":" + crminute;;
				} else {
					return crmonth + "月" + crday + "日" + " " + crhour + ":" + crminute;
				}
			} else {
				/* 月不相邻 */
				return crmonth + "月" + crday + "日" + " " + crhour + ":" + crminute;
			}
		} else {
			/* 月相同 */
			if (crday != currday) {
				/* 日不同 */
				var daydis = currday - crday;//日差
				if (daydis == 1) {
					/* 相邻日 */
					var hourdis = 24 - crhour + currhour;//时差
					if (hourdis == 1) {
						/* 时相连 */
						var mindis = 60 - crminute + currminute;
						if (mindis > 60) {
							return hourdis + "小时前";
						} else {
							return mindis + "分钟前";
						}
					} else if (hourdis == 2) {
						return hourdis + "小时前";
					} else {
						return "昨天" + " " + crhour + ":" + crminute;
					}
				} else if (daydis == 2) {
					return "前天" + " " + crhour + ":" + crminute;
				} else {
					return crmonth + "月" + crday + "日" + " " + crhour + ":" + crminute;
				}
			} else {
				/* 日相同 */
				var hourdis = currhour - crhour;//时差
				if (hourdis == 0) {
					/* 时相同 */
					var minutedis = currminute - crminute;//分差
					if (minutedis == 0) {
						/* 分相同 */
						return "刚刚";
					} else {
						/* 分不同 */
						return minutedis + "分钟前";
					}
				} else if (hourdis == 1) {
					/* 小时相邻 */
					var mindis = 60 - crminute + currminute;//分差
					if (mindis > 60) {
						return hourdis + "小时前";
					} else {
						return mindis + "分钟前";
					}

				} else if (hourdis < 12) {
					/* 十二小时内 */
					return hourdis + "小时前";
				} else {
					/* 十二小时外 */
					return crhour + ":" + crminute;
				}
			}
		}
	}
}

/* 返回某一年的某一月有几天 */
function getDayOfMonth(year, month) {
	if (month == 2) {
		if (year % 4 == 0) {
			return 28;
		} else {
			return 29;
		}
	} else if (month == 4 || month == 6 || month == 9 || month == 11) {
		return 30;
	} else {
		return 31;
	}
} 

大家看得懂吗？