專案中需要用到日期的格式轉化及相關的加減，根據需要的情況，整理了部分方法。並列出date的構造方法及方法以作記錄。

一、以下是根據小程式demo中util.js檔案修改的

const formatTime = date => {
  const year = date.getFullYear()
  const month = date.getMonth() + 1
  const day = date.getDate()
  const hour = date.getHours()
  const minute = date.getMinutes()
  const second = date.getSeconds()

  return
 
 [year, month, day].map(formatNumber).join('/') + ' ' + [hour, minute, second].map(formatNumber).join(':')
}
//獲取當前日期，以“/”連線
const formatDate = date => {
    const year = date.getFullYear()
    const month = date.getMonth() + 1
    const day = date.getDate()

    return [year, month, day].map(formatNumber).join('/'
 
)
}
//獲取當前日期，以“-”連線
const formatDateByH = date => {
    const year = date.getFullYear()
    const month = date.getMonth() + 1
    const day = date.getDate()

    return [year, month, day].map(formatNumber).join('-')
}
//將string格式日期轉換為“/”連線只包含月日的日期
const formatDateToSimple = data => {
    var date = new
 
 Date(Date.parse(data));
    const month = date.getMonth() + 1
    const day = date.getDate()

    return [month, day].join('/')
}
//獲取string格式日期的星期
const formatDateToWeek = data => {
    var date = new Date(Date.parse(data));
    const month = date.getDay();
    var weekDay ;
    switch (month){
        case 0:
            weekDay = '週日';
            break;
        case 1:
            weekDay = '週一';
            break;
        case 2:
            weekDay = '週二';
            break;
        case 3:
            weekDay = '週三';
            break;
        case 4:
            weekDay = '週四';
            break;
        case 5:
            weekDay = '週五';
            break;
        case 6:
            weekDay = '週六';
            break
    }
    return weekDay;
}

//日期的加減
const addDay = data => {
    //下面的不是時間戳，是時間戳*1000
    var timestamp = Date.parse(new Date());
    var newTimestamp = timestamp + data * 24 * 60 * 60 * 1000;
    var date = new Date(newTimestamp);

    const year = date.getFullYear();
    const month = date.getMonth() + 1;
    const day = date.getDate();

    return [year, month, day].map(formatNumber).join('-');
}

//月份的加減
const addMonth = num => {
    if(typeof num == "string"){
        num = parseInt(num);
    }
    var date = new Date();
    const curYear = date.getFullYear();
    const curMonth = date.getMonth() + 1;
    const curDay = date.getDate();
    let month = (curMonth + num - 1) % 12;
    let year = curYear + (curMonth + num - month)/12;
    let days = curDay;
    date = new Date(year, month, days);
    year = date.getFullYear();
    month = date.getMonth() + 1;
    const day = date.getDate();

    return [year, month, day].map(formatNumber).join('-')
}
//月份第幾天增加後獲取月份的第幾天
const getDayByAddDay = data => {
    //下面的不是時間戳，是時間戳*1000
    var timestamp = Date.parse(new Date());
    var newTimestamp = timestamp + data * 24 * 60 * 60 * 1000;
    var date = new Date(newTimestamp);

    return date.getDate();
}

const formatNumber = n => {
    n = n.toString()
    return n[1] ? n : '0' + n
}

module.exports = {
    formatTime: formatTime,
    formatDate: formatDate,
    formatDateByH: formatDateByH,
    addDay: addDay,
    addMonth: addMonth,
    getDayByAddDay: getDayByAddDay,
    formatDateToSimple: formatDateToSimple,
    formatDateToWeek: formatDateToWeek,
}

二、主要用到函式Date。
1、建構函式

interface DateConstructor {
    new(): Date;
    new(value: number): Date;
    new(value: string): Date;
    new(year: number, month: number, date?: number, hours?: number, minutes?: number, seconds?: number, ms?: number): Date;
    (): string;
    readonly prototype: Date;
    /**
      * Parses a string containing a date, and returns the number of milliseconds between that date and midnight, January 1, 1970.
      * @param s A date string
      */
    parse(s: string): number;
    /**
      * Returns the number of milliseconds between midnight, January 1, 1970 Universal Coordinated Time (UTC) (or GMT) and the specified date.
      * @param year The full year designation is required for cross-century date accuracy. If year is between 0 and 99 is used, then year is assumed to be 1900 + year.
      * @param month The month as an number between 0 and 11 (January to December).
      * @param date The date as an number between 1 and 31.
      * @param hours Must be supplied if minutes is supplied. An number from 0 to 23 (midnight to 11pm) that specifies the hour.
      * @param minutes Must be supplied if seconds is supplied. An number from 0 to 59 that specifies the minutes.
      * @param seconds Must be supplied if milliseconds is supplied. An number from 0 to 59 that specifies the seconds.
      * @param ms An number from 0 to 999 that specifies the milliseconds.
      */
    UTC(year: number, month: number, date?: number, hours?: number, minutes?: number, seconds?: number, ms?: number): number;
    now(): number;
}

2、Date的方法

interface Date {
    /** Returns a string representation of a date. The format of the string depends on the locale. */
    toString(): string;
    /** Returns a date as a string value. */
    toDateString(): string;
    /** Returns a time as a string value. */
    toTimeString(): string;
    /** Returns a value as a string value appropriate to the host environment's current locale. */
    toLocaleString(): string;
    /** Returns a date as a string value appropriate to the host environment's current locale. */
    toLocaleDateString(): string;
    /** Returns a time as a string value appropriate to the host environment's current locale. */
    toLocaleTimeString(): string;
    /** Returns the stored time value in milliseconds since midnight, January 1, 1970 UTC. */
    valueOf(): number;
    /** Gets the time value in milliseconds. */
    getTime(): number;
    /** Gets the year, using local time. */
    getFullYear(): number;
    /** Gets the year using Universal Coordinated Time (UTC). */
    getUTCFullYear(): number;
    /** Gets the month, using local time. */
    getMonth(): number;
    /** Gets the month of a Date object using Universal Coordinated Time (UTC). */
    getUTCMonth(): number;
    /** Gets the day-of-the-month, using local time. */
    getDate(): number;
    /** Gets the day-of-the-month, using Universal Coordinated Time (UTC). */
    getUTCDate(): number;
    /** Gets the day of the week, using local time. */
    getDay(): number;
    /** Gets the day of the week using Universal Coordinated Time (UTC). */
    getUTCDay(): number;
    /** Gets the hours in a date, using local time. */
    getHours(): number;
    /** Gets the hours value in a Date object using Universal Coordinated Time (UTC). */
    getUTCHours(): number;
    /** Gets the minutes of a Date object, using local time. */
    getMinutes(): number;
    /** Gets the minutes of a Date object using Universal Coordinated Time (UTC). */
    getUTCMinutes(): number;
    /** Gets the seconds of a Date object, using local time. */
    getSeconds(): number;
    /** Gets the seconds of a Date object using Universal Coordinated Time (UTC). */
    getUTCSeconds(): number;
    /** Gets the milliseconds of a Date, using local time. */
    getMilliseconds(): number;
    /** Gets the milliseconds of a Date object using Universal Coordinated Time (UTC). */
    getUTCMilliseconds(): number;
    /** Gets the difference in minutes between the time on the local computer and Universal Coordinated Time (UTC). */
    getTimezoneOffset(): number;
    /**
      * Sets the date and time value in the Date object.
      * @param time A numeric value representing the number of elapsed milliseconds since midnight, January 1, 1970 GMT.
      */
    setTime(time: number): number;
    /**
      * Sets the milliseconds value in the Date object using local time.
      * @param ms A numeric value equal to the millisecond value.
      */
    setMilliseconds(ms: number): number;
    /**
      * Sets the milliseconds value in the Date object using Universal Coordinated Time (UTC).
      * @param ms A numeric value equal to the millisecond value.
      */
    setUTCMilliseconds(ms: number): number;

    /**
      * Sets the seconds value in the Date object using local time.
      * @param sec A numeric value equal to the seconds value.
      * @param ms A numeric value equal to the milliseconds value.
      */
    setSeconds(sec: number, ms?: number): number;
    /**
      * Sets the seconds value in the Date object using Universal Coordinated Time (UTC).
      * @param sec A numeric value equal to the seconds value.
      * @param ms A numeric value equal to the milliseconds value.
      */
    setUTCSeconds(sec: number, ms?: number): number;
    /**
      * Sets the minutes value in the Date object using local time.
      * @param min A numeric value equal to the minutes value.
      * @param sec A numeric value equal to the seconds value.
      * @param ms A numeric value equal to the milliseconds value.
      */
    setMinutes(min: number, sec?: number, ms?: number): number;
    /**
      * Sets the minutes value in the Date object using Universal Coordinated Time (UTC).
      * @param min A numeric value equal to the minutes value.
      * @param sec A numeric value equal to the seconds value.
      * @param ms A numeric value equal to the milliseconds value.
      */
    setUTCMinutes(min: number, sec?: number, ms?: number): number;
    /**
      * Sets the hour value in the Date object using local time.
      * @param hours A numeric value equal to the hours value.
      * @param min A numeric value equal to the minutes value.
      * @param sec A numeric value equal to the seconds value.
      * @param ms A numeric value equal to the milliseconds value.
      */
    setHours(hours: number, min?: number, sec?: number, ms?: number): number;
    /**
      * Sets the hours value in the Date object using Universal Coordinated Time (UTC).
      * @param hours A numeric value equal to the hours value.
      * @param min A numeric value equal to the minutes value.
      * @param sec A numeric value equal to the seconds value.
      * @param ms A numeric value equal to the milliseconds value.
      */
    setUTCHours(hours: number, min?: number, sec?: number, ms?: number): number;
    /**
      * Sets the numeric day-of-the-month value of the Date object using local time.
      * @param date A numeric value equal to the day of the month.
      */
    setDate(date: number): number;
    /**
      * Sets the numeric day of the month in the Date object using Universal Coordinated Time (UTC).
      * @param date A numeric value equal to the day of the month.
      */
    setUTCDate(date: number): number;
    /**
      * Sets the month value in the Date object using local time.
      * @param month A numeric value equal to the month. The value for January is 0, and other month values follow consecutively.
      * @param date A numeric value representing the day of the month. If this value is not supplied, the value from a call to the getDate method is used.
      */
    setMonth(month: number, date?: number): number;
    /**
      * Sets the month value in the Date object using Universal Coordinated Time (UTC).
      * @param month A numeric value equal to the month. The value for January is 0, and other month values follow consecutively.
      * @param date A numeric value representing the day of the month. If it is not supplied, the value from a call to the getUTCDate method is used.
      */
    setUTCMonth(month: number, date?: number): number;
    /**
      * Sets the year of the Date object using local time.
      * @param year A numeric value for the year.
      * @param month A zero-based numeric value for the month (0 for January, 11 for December). Must be specified if numDate is specified.
      * @param date A numeric value equal for the day of the month.
      */
    setFullYear(year: number, month?: number, date?: number): number;
    /**
      * Sets the year value in the Date object using Universal Coordinated Time (UTC).
      * @param year A numeric value equal to the year.
      * @param month A numeric value equal to the month. The value for January is 0, and other month values follow consecutively. Must be supplied if numDate is supplied.
      * @param date A numeric value equal to the day of the month.
      */
    setUTCFullYear(year: number, month?: number, date?: number): number;
    /** Returns a date converted to a string using Universal Coordinated Time (UTC). */
    toUTCString(): string;
    /** Returns a date as a string value in ISO format. */
    toISOString(): string;
    /** Used by the JSON.stringify method to enable the transformation of an object's data for JavaScript Object Notation (JSON) serialization. */
    toJSON(key?: any): string;
}