计算自特定日期以来的年月

Question

我刚开始使用 Java Script。我正在尝试提出一个简单的解决方案：当前日期 - 格式为“2018 年 1 月 4 日”的指示日期 = 自指示日期以来的年月。我查看了Datejs，但无法弄清楚如何使用它来进行简单的数学日期计算。我想出了这个，但我不确定这是否是可行的方法。欢迎提出建议。var dPast = 'January 4, 2018'var d1 = new Date(); //"now"var d2 = new Date(dPast);var dCalc = Math.abs((d1-d2)/31556952000);   // difference in millisecondsvar diff = Math.round(10 * dCalc)/10;   // difference in years rounded to tenthalert('It has been ' + diff + ' years since ' + dPast);

Answer 1

最好先从当前日期中减去指定日期的毫秒数，然后将其格式化为您想要的输出。

var dPast = 'January 5, 2018';

var indicatedD = new Date(dPast);

var d = new Date();

// subtract the current time's milliseconds from the dPast date's.

var elapsed = new Date(d.getTime() - indicatedD.getTime());

// get the years.

var years = Math.abs(elapsed.getUTCFullYear() - 1970);

console.log('It has been ' + years + ' years since ' + dPast);

因为你刚刚起步，所以最好自己探索，但当你适应后，我建议你使用日期库，例如moment.js，因为它更可靠并且有大量内置方法会让你的生活更轻松。

Answer 2

可能你可能想检查 moment.js。它只有 2.6kb 大小，或者你可以使用 cdn

<script src="//cdnjs.cloudflare.com/ajax/libs/moment.js/2.13.0/moment.min.js"></script>

检查diff功能

var dPast = 'January 4, 2018'

var todaysDate = moment(new Date()); //"now"

var pastDate = moment(new Date(dPast));

var years = todaysDate.diff(pastDate, 'years');

var months = todaysDate.diff(pastDate, 'months');

console.log(years + ' years, ' + months % 12 + ' months');

<script src="//cdnjs.cloudflare.com/ajax/libs/moment.js/2.13.0/moment.min.js"></script>

Answer 3

原始解决方案可在此处找到：https ://forums.getdrafts.com/t/calculate-years-and-months-since-a-specific-date/8082/3

这段代码是一个进步，因为我想让初学者的事情变得简单。然而，我是一步一步去理解的。我会在这里留下足迹，供我自己参考，也供以后的人参考。

/*********

Day.js is a minimalist JavaScript library that parses, validates, manipulates, and displays dates and times for modern browsers with a largely Moment.js-compatible API.

Step 1: Download the dayjs.min.js file from the JSDelivr site: https://www.jsdelivr.com/package/npm/dayjs

Step 2 : Save the downloaded file to the Drafts/Library/Scripts folder in iCloud. 

*/

require('dayjs.min.js'); // Tell Drafts to use Dayjs script

let dPast = 'December 4, 2017'; // set the date from the past

let d1 = dayjs(); // tell Dayjs to parse the date

let d2 = dayjs(dPast); // set the current date

/******

* Math.round() - is a function that is used to return a number rounded to the nearest integer (whole) value.

* To get the difference in months, pass the month as the second argument. By default, dayjs#diff will truncate the result to zero decimal places, returning an integer. If you want a floating point number, pass true as the third argument.

*Read more: https://day.js.org/docs/en/display/difference#docsNav

*/

let m = Math.round(d1.diff(d2, 'month', true));

/******

* Divide the number of months (obtained earlier) by 12 to see how many years. This number will be rounded to an integer (whole number). If the result is less than 1 (years) the rounded number will be set to 0. For example 11/12 = 0.916666667 This will be rounded to 0.

*/

let y = Math.floor(m/12); 

if (y == 0) {

  alert(`\n${m} months since ${dPast}`); // Alert that "x" number of months but no years have passed since the indicated date.

}

/* Remainder

An amount left over after division (happens when the first number does not divide exactly by the other). Example: 19 cannot be divided exactly by 5. The closest you can get without going over is 3 x 5 = 15, which is 4 less than 19. So 4 is the remainder.

In JavaScript, the remainder operator (%) returns the remainder left over when one operand is divided by a second operand. It always takes the sign of the dividend.

*/

else {

  m = m % 12;

  if (m == 0) {

    alert(`${y} years since ${dPast}`); //If the remainder is 0 than a whole year(s) have passed since the indicated date but no months.

  }

  else {

    alert(`${y} years, ${m} months since ${dPast}`); // Years and months since the indicated date.

  }

}

Answer 4

这段代码经过测试可以运行，可以精确到分钟。

/**

 * 计算日期&时间间隔/推算几天前后是哪一天

 * @author 江村暮

 */

//平年

const ordinaryYearMonth: Array<any> = [null, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

//闰年

const leapYearMonth: Array<any> = [null, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]

/**

 * 是否为闰年

 **/

const isLeap = (year: number): boolean => {

    if (year % 400 === 0 && year % 100 === 0) return true

    if (year % 4 === 0 && year % 100 !== 0) return true

    return false

}

//解析时间串

type Num = number

const parseTime = (time: string): {

    hour: Num;

    min: Num

} => {

    var bound: Num = time.indexOf(':')

    return {

        hour: parseInt(time.substring(0, bound)),

        min: parseInt(time.substring(bound + 1))

    }

}

//解析日期串

const parseDate = (date = '2020-03-06'): Readonly<{

    year: number;

    month: number;

    day: number;

    isLeap: boolean

}> => {

    var match = /(\d{4})-(\d{2})-(\d{2})/.exec(date);

    if (!match) throw Error

    return {

        year: parseInt(match[1]),

        month: parseInt(match[2].replace(/^0/, '')),

        day: parseInt(match[3].replace(/^0/, '')),

        isLeap: isLeap(parseInt(match[1]))

    }

}

const calDiffer = (

    defaultDateEarly: string,

    defaultDateLate: string,

    defaultTimeEarly?: string,

    defaultTimeLate?: string

): {

    day: number,

    hour: number,

    min: number,

    overflowHour: number,

    overflowMin: number

} => {

    var dateEarly = parseDate(defaultDateEarly)

        , dateLate = parseDate(defaultDateLate)

        , diffDay: number;

    //两个日期在同一年

    if (dateLate.year === dateEarly.year) {

        var numOfEarlyMonthDay = dateEarly.isLeap ? leapYearMonth[dateEarly.month] : ordinaryYearMonth[dateEarly.month]

        // 两个日期在同一月份

        if (dateLate.month === dateEarly.month) {

            diffDay = dateLate.day - dateEarly.day

        } else {

            diffDay = dateLate.day + numOfEarlyMonthDay - dateEarly.day;//两个日期所在月的非整月天数和

            for (let i = dateEarly.month; i < dateLate.month - 1; i++) {

                diffDay += (dateLate.isLeap) ? leapYearMonth[i] : ordinaryYearMonth[i]

            }

        }

    } else {

        //这一年已过天数

        var lateYearDay = dateLate.day;

        for (let i = dateLate.month - 1; i >= 1; i--) {

            lateYearDay += (dateLate.isLeap) ? leapYearMonth[i] : ordinaryYearMonth[i]

        }

        console.log(lateYearDay)

        //那一年剩下天数

        var earlyYearDay = 0

        for (let i = 13 - dateEarly.month; i >= 1; i--) {

            earlyYearDay += (dateLate.isLeap) ? leapYearMonth[i] : ordinaryYearMonth[i]

        }

        earlyYearDay -= dateEarly.day

        console.log(earlyYearDay)

        //相隔年份天数，如：年份为2010 - 2020，则计算2011 - 2019的天数

        var diffYear: number[] = [];

        for (let i = 0; i <= dateLate.year - dateEarly.year - 1; i++) {

            diffYear.push(dateEarly.year + i + 1)

        }

        diffDay = earlyYearDay + lateYearDay

        diffYear.map(year => {

            diffDay += isLeap(year) ? 366 : 365

        })

    }

    //计算这天剩下的时间与那天已经过的分钟之和

    var timeEarly = parseTime(defaultTimeEarly || '00:00'),

        timeLate = parseTime(defaultTimeLate || '00:00');

    var overflowDiffMin = 60 * (25 - timeEarly.hour + timeLate.hour) + 60 - timeEarly.min + timeLate.min

    var diffMin = (diffDay - 1) * 1440 + overflowDiffMin

    console.log(timeEarly, timeLate, diffMin)

    return {

        day: diffDay,

        overflowHour: Math.floor(diffMin/60) - diffDay * 24,

        overflowMin: diffMin % 60,//(overflowDiffMin - 1440 * diffDay) % 60,

        hour: Math.floor(diffMin/60),

        min: diffMin % 60

    }

}

export { calDiffer }