详解js中常规日期格式处理、月历渲染和倒计时函

/**
 * [zeroPadding 小于10的数字补0，必填]
 * @param {[Int]} value [description]
 * @return {[String]} [description]
 */
export function zeroPadding(value){
 return value < 10 ? `0${value}` : value;
}

/**
 * [_isDateStrSeparatorCh 判断日期格式字符串的分隔符是否是中文]
 * @param {[String]} str [必填]
 * @return {[String]} [分隔符]
 */
function _getDateStrSeparator(str, startIndex, endIndex) {
 startIndex = startIndex ? startIndex : 4;
 endIndex = endIndex ? endIndex : 5;
 let separator = str.slice(startIndex, endIndex);
 if (separator === '年' || separator === '月' ) {
 separator = 'Ch';
 }
 return separator;
}

/**
 * [_isDateStrSeparatorCh 判断日期格式字符串的分隔符是否是中文]
 * @param {[String]} str [必填]
 * @return {[String]} [分隔符]
 */
function _isDateStrSeparatorCh(str) {
 if ( str.indexOf('年')!=-1 || str.indexOf('月')!=-1 ) {
 return true;
 }
 return false;
}

/**
 * [getFormatDateStr 获得指定日期格式的字符串]
 * @param {[String or Date]} date [要转换的日期，必填]
 * @param {[String]} dateFormatStr [要转化的目标格式，必填，2016-11-22之间的分隔符可任意，可选项：
 * 'yyyy-mm-dd hh:mm:ss','yyyy/mm/dd hh:mm:ss','yyyy.mm.dd hh:mm:ss','yyyy年mm月dd hh:mm:ss',
 * 'yyyy-mm-dd hh:mm',
 * 'mm-dd hh:mm',
 * 'yyyy-mm-dd',
 * 'mm-dd',
 * 'hh:mm:ss',
 * 'hh:mm'
 * ]
 * @return {[String]}  [时间格式字符串]
 */
export function getFormatDateStr(date, dateFormatStr) {

 if ( !(date instanceof Date) ) {
 if ( date.indexOf('-') != -1 ) {
 date.replace(/\-/g,'/');
 }
  date = new Date(date);
 }

 dateFormatStr = dateFormatStr.toLowerCase();
 if (!dateFormatStr){
 return false;
 }

 let returnStr = '',
 separator = _getDateStrSeparator(dateFormatStr),
 year = date.getFullYear(),
  month = date.getMonth() + 1,
  day = date.getDate(),
  hour = date.getHours(),
  minute = date.getMinutes(),
 second = date.getSeconds();

 if ( /^yyyy(.{1})mm(.{1})dd hh:mm:ss$/.test(dateFormatStr) ) {
 if (_isDateStrSeparatorCh(dateFormatStr)) {
 returnStr = `${year}年${zeroPadding(month)}月${zeroPadding(day)}日`;
 } else {
 separator =
 returnStr = `${year}${separator}${zeroPadding(month)}${separator}${zeroPadding(day)}`;
 }
 returnStr += ` ${zeroPadding(hour)}:${zeroPadding(minute)}:${zeroPadding(second)}`;
 } else if ( /^yyyy(.{1})mm(.{1})dd hh:mm$/.test(dateFormatStr) ) {
 if (_isDateStrSeparatorCh(dateFormatStr)) {
 returnStr = `${year}年${zeroPadding(month)}月${zeroPadding(day)}日`;
 } else {
 returnStr = `${year}${separator}${zeroPadding(month)}${separator}${zeroPadding(day)}`;
 }
 returnStr += ` ${zeroPadding(hour)}:${zeroPadding(minute)}`;
 } else if ( /^mm(.{1})dd hh:mm$/.test(dateFormatStr) ) {
 if (_isDateStrSeparatorCh(dateFormatStr)) {
 returnStr = `${zeroPadding(month)}月${zeroPadding(day)}日`;
 } else {
 separator = _getDateStrSeparator(dateFormatStr, 2, 3);
 returnStr = `${zeroPadding(month)}${separator}${zeroPadding(day)}`;
 }
 returnStr += ` ${zeroPadding(hour)}:${zeroPadding(minute)}`;
 } else if ( /^yyyy(.{1})mm(.{1})dd$/.test(dateFormatStr) ) {
 if (_isDateStrSeparatorCh(dateFormatStr)) {
 returnStr = `${year}年${zeroPadding(month)}月${zeroPadding(day)}日`;
 } else {
 returnStr = `${year}${separator}${zeroPadding(month)}${separator}${zeroPadding(day)}`;
 }
 } else if ( /^mm(.{1})dd$/.test(dateFormatStr) ) {
 if (_isDateStrSeparatorCh(dateFormatStr)) {
 returnStr = `${zeroPadding(month)}月${zeroPadding(day)}日`;
 } else {
 separator = _getDateStrSeparator(dateFormatStr, 2, 3);
 returnStr = `${zeroPadding(month)}${separator}${zeroPadding(day)}`;
 }
 } else if ( /^hh:mm:ss$/.test(dateFormatStr) ) {
 returnStr = `${zeroPadding(hour)}:${zeroPadding(minute)}:${zeroPadding(second)}`;
 } else if ( /^hh:mm$/.test(dateFormatStr) ) {
 returnStr = `${zeroPadding(hour)}:${zeroPadding(minute)}`;
 }

 return returnStr;

}

/**
 * [getDayPrevAfter 获得n天前/后的日期]
 * @param {[String]} date [日期，非必填参数，表示调用时的时间]
 * @param {[String]} type [前一天还是后一天，非必填参数，默认后一天]
 * @param {[Int]} daysNum [天数，非必填参数，默认一天]
 * @return {[Date]}  [description]
 */
export function getDayPrevAfter(date, type, daysNum) {

 date = date ? date : new Date();
 type = type ? type : 'after';
 daysNum = daysNum ? daysNum : 1;

 if ( !(date instanceof Date) ) {
 if ( date.indexOf('-') != -1 ) {
 date.replace(/\-/g,'/');
 }
 date = new Date(date);
 }

 let returnDate = date;
 if (type === 'prev') {
 returnDate = new Date(date.getTime() - (daysNum * 24 * 60 * 60 * 1000));
 } else if (type === 'after') {
 returnDate = new Date(date.getTime() + (daysNum * 24 * 60 * 60 * 1000));
 }
 return returnDate;

}

/**
 * [formatDateWithTimeZone 格式化日期带时区，ISO 8601]
 * @param {[Date]} date [日期，非必填参数，表示调用时的时间]
 * @return {[String]} [ISO 8601格式的日期，example: 2016-11-21T14:09:15+08:00]
 */
export function formatDateWithTimeZone(date) {

 date = date ? date : new Date();
 if ( !(date instanceof Date) ) {
 if ( date.indexOf('-') != -1 ) {
 date.replace(/\-/g,'/');
 }
 date = new Date(date);
 }

 let tzo = -date.getTimezoneOffset(),
 dif = tzo >= 0 ? '+' : '-',
 pad = function (num) {
  let norm = Math.abs(Math.floor(num));
  return zeroPadding(norm);
 };
 return `${date.getFullYear()}-${pad(date.getMonth() + 1)}-${pad(date.getDate())}T${pad(date.getHours())}:${pad(date.getMinutes())}:${pad(date.getSeconds())}${dif}${pad(tzo / 60)}:${pad(tzo % 60)}`;

}

/**
 * [countDownBySecond 倒计时]
 * @param {[Int]} restSeconds [剩余秒数，必填]
 * @param {[Int]} timeInterval [时间间隔，非必填，默认1000ms]
 * @param {[Function]} func [每倒计时一次，就需要执行一次的回调函数名，非必填]
 * @param {[Function]} endFun [倒计时结束需要执行的函数名，非必填]
 * @return {[null]} [无返回值]
 */
export function countDownBySecond(restSeconds, timeInterval, func, endCallback) {
 let timer = null;
 let total = restSeconds;
 timeInterval = timeInterval ? timeInterval : 1000;
 timer = setInterval(function() {
 --total;
 if (total <= 0) {
  clearInterval(timer);
  endCallback && endCallback();
 }
 func && func(total);
 }, timeInterval);
}

/**
 * [monthSize 获得指定日期所在月的天数]
 * @param {[Date]} oDate [指定的日期，非必填，默认为当天]
 * @return {[Int]} [总天数]
 */
function monthSize(oDate) {
 oDate = oDate ? oDate : new Date();
 let year = oDate.getFullYear(),
 month = oDate.getMonth(),
 _oDate = new Date();
 _oDate.setFullYear(year);
 _oDate.setMonth(month + 1, 0);
 return _oDate.getDate();
}

/**
 * [getCalendarMonth 获得指定日期所在月的第一周到第四/五周的数据组合，形如：
 * [{
 "date": "2016/10/30", //日期字符串
 "dateNum": 30, //日
 "isCurMonth": false, //是否当前月
 "weekIndex": 0 //是本月的第几周，下标从0开始
 },{
 "date": "2016/10/31",
 "dateNum": 31,
 "isCurMonth": false,
 "weekIndex": 0
 },{
 "date": "2016/11/1",
 "dateNum": 1,
 "day": 2,
 "isCurMonth": true,
 "isToday": false,
 "weekIndex": 0
 }]
 ]
 * @param {[Date]} param [指定的日期，非必填，默认为当天]
 * @return {[Array]} [获得指定日期所在月的第一周到第四/五周的数据组合]
 */
export function getCalendarMonth(date) {
 date = date ? date : new Date();
 let y = date.getFullYear();
 let m = date.getMonth();
 let _m;
 let firstDay = new Date(y, m, 1).getDay(); //当月第一天 周期
 let days = monthSize(date);//当月天数
 let prevMonthDays = monthSize(new Date(y, m - 1));//上月天数
 let initPrevDay = prevMonthDays - firstDay;
 let lines = Math.ceil((firstDay + days) / 7);
 _m = new Array(lines * 7);
 let nextMonthDay = 0;

 for (let i = 0; i < _m.length; i++) {
 let weekIndex = parseInt(i / 7);
 if (i < firstDay) {
  let date = ++initPrevDay;
  if (m === 0 && date > 7) {
  _m[i] = {
   isCurMonth: false,
   dateNum: date,
   weekIndex,
   date: `${y - 1}/${12}/${date}`
  };
  } else {
  _m[i] = {
   isCurMonth: false,
   dateNum: date,
   weekIndex,
   date: `${y}/${m}/${date}`
  };
  }
 } else if (i >= (firstDay + days)) {
  let date = ++nextMonthDay;

  if (m === 11 && date <= 7) {
  _m[i] = {
   isCurMonth: false,
   dateNum: date,
   weekIndex,
   date: `${y + 1}/${1}/${date}`
  };
  } else {
  _m[i] = {
   isCurMonth: false,
   dateNum: date,
   weekIndex,
   date: `${y}/${m + 2}/${date}`
  };
  }
 } else {
  let _date = i - firstDay + 1;
  let today = new Date();
  let today_y = today.getFullYear();
  let today_m = today.getMonth();
  let today_d = today.getDate();
  let isToday = today_y === y && today_m === m && today_d === _date ? true : false;
  _m[i] = {
  dateNum: _date, //日期
  day: i % 7, //周期
  weekIndex,
  isCurMonth: true,
  isToday,
  date: `${y}/${m + 1}/${_date}`
  };
 }
 }
 return _m;
}

/**
 * [getOneDateWeekIndex 获得指定的某天所在该月的第几周，下标从0开始]
 * @param {[Date]} date [指定的日期，非必填，默认为当天]
 * @return {[Int]} [在该月的第几周]
 */
export function getOneDateWeekIndex(date) {
 date = date ? date : new Date();
 let monthDays = getCalendarMonth(date);
 let dateString = getFormatDateStr(date, '/', true, false, false);
 let returnDate = monthDays.filter(item => {
 return item.date === dateString;
 });
 let weekIndex = returnDate[0].weekIndex;
 return weekIndex ? weekIndex : 0;
}