Moment.js & Day.js 时间日期类库

前言

在项目开发的时候，日期时间处理是一个非常常见的需求。然而问题在于 JS 原生的 Date 对象操作其实不太方便，因此延伸出了许多三方库用于封装 Date 对象，以及推动新的日期标准 Intl 的制定和实现。

本篇挑出三方库中大名鼎鼎的 moment.js 和 day.js 做介绍

正文

0. 环境配置

本篇实例运行在 node 环境，先来配置一下环境和依赖

0.1 安装依赖

$ yarn init -y  # 初始化项目
$ yarn add moment dayjs  # 安装核心依赖

以及运行测试命令

• package.json

{
  "name": "moment-dayjs",
  "version": "1.0.0",
  "main": "index.js",
  "license": "MIT",
  "scripts": {
    "dayjs": "node src/dayjs/index.js",
    "moment": "node src/moment/index.js"
  },
  "dependencies": {
    "dayjs": "^1.10.4",
    "moment": "^2.29.1"
  }
}

0.2 辅助工具函数

同时我们先定义一下后面会用到的工具函数，避免误解

• src/utils/group.js

const emptyFn = () => {}

const log = console.log

function group(name, cb = emptyFn) {
  console.group(name)
  cb()
  console.groupEnd()
}

module.exports = {
  log,
  group,
}

log 为 console.log 的别名，group 方法对 console.group 稍微封装一下

1. Moment.js

第一个我们首先来介绍 Moment.js 提供的日期时间操作能力，主要分成以下几个大类介绍一些比较常见的功能需求和用法

• 创建时间日期对象
• 获取/设置属性
• 日期操作(加、减、对齐、选择)
• 查询(判断、比较)
• 格式化输出

1.1 创建时间日期对象

一开始当然是先创建 moment.js 定义的新的时间对象，直接使用 moment 方法构造

• src/moment/1_parse.js

const moment = require('moment')
const { log, group } = require('../utils/group')

group('moment.js parse', () => {
  group('moment', () => {
    log(`moment():                            ${moment().format()}`)
    log(`moment('2021-11-01'):                ${moment('2021-11-01').format()}`)
    log(`moment('2021-11-01 23:59:59'):       ${moment('2021-11-01 23:59:59').format()}`)
    log(`moment('20211101T235959'):           ${moment('20211101T235959').format()}`)
    log(`moment('01-11-2021', 'DD-MM-YYYY'):  ${moment('01-11-2021', 'DD-MM-YYYY').format()}`)
    log(`moment([2021, 10, 1, 23, 59, 59]):   ${moment([2021, 10, 1, 23, 59, 59]).format()}`)
  })
  
// ...

传入的内容还是比较自由，主要以字符串描述为主，可用函数标签如下

moment()        // 当前时间
moment(string)  // UTC 或 ISO 格式的时间描述字符串
moment(string, string)  // 第二个参数作为自定义字符串模版
moment(number)  // 传入时间戳
moment(array)   // 按序传入时间描述

看输出吧

moment.js parse
  moment
    moment():                            2021-05-21T14:37:10+08:00
    moment('2021-11-01'):                2021-11-01T00:00:00+08:00
    moment('2021-11-01 23:59:59'):       2021-11-01T23:59:59+08:00
    moment('20211101T235959'):           2021-11-01T23:59:59+08:00
    moment('01-11-2021', 'DD-MM-YYYY'):  2021-11-01T00:00:00+08:00
    moment([2021, 10, 1, 23, 59, 59]):   2021-11-01T23:59:59+08:00

还是比较简单直接的，另外由于 moment 对象的操作常常会直接改变对象实例，所以我们还需要另一个 clone 方法来拷贝对象进行复用

// ...

  group('clone', () => {
    const m1 = moment()
    const m2 = moment(m1)
    const m3 = m2.clone()
    log(`m1:  ${m1.toString()}`)
    log(`m2:  ${m2.toString()}`)
    log(`m3:  ${m3.toString()}`)
    log(`m1 === m2:                        ${m1 === m2}`)
    log(`m1 === m3:                        ${m1 === m3}`)
    log(`m2 === m3:                        ${m2 === m3}`)
    log(`m1.toString() === m2.toString():  ${m1.toString() === m2.toString()}`)
    log(`m1.toString() === m3.toString():  ${m1.toString() === m3.toString()}`)
    log(`m2.toString() === m3.toString():  ${m2.toString() === m3.toString()}`)
  })
})

我们可以直接调用 moment(instance) 或是 moment.clone() 来创建实例副本

1.2 获取/设置属性

第二个模块则是介绍对于时间日期属性的获取和直接设置

首先我们给出几个函数标签

// moment# 表示 moment.prototype 的原型方法
moment#[unit]()   // 获取指定单位(unit) 的值
moment#set(unit)  // 获取指定单位(unit) 的值
moment#[unit](val)     // 设置指定单位(unit) 的值
moment#set(unit, val)  // 设置指定单位(unit) 的值

我们可以透过直接调用指定单位来获取/设置属性值，或是调用 get/set 方法并传入目标属性字符串来进行调用

• src/moment/2_getter_setter.js

const moment = require('moment')
const { log, group } = require('../utils/group')

group('moment.js getter/setter', () => {
  const origin = moment('2021-11-01 23:59:59.699')

  let time = origin.clone()

  group('second', () => {
    log(`time:              ${time}`)
    log(`time.second():     ${time.second()}`)
    log(`time.second(996):  ${time.second(30)}`)
    log(`time.second():     ${time.second()}`)
  })

  group('hour', () => {
    log(`time:          ${time}`)
    log(`time.hour():   ${time.hour()}`)
    log(`time.hour(1):  ${time.hour(1)}`)
    log(`time.hour():   ${time.hour()}`)
  })

  time = origin.clone()

  group('get/set', () => {
    log(`current time:             ${time}`)
    log(`time.get('year'):         ${time.get('year')}`)
    log(`time.get('month'):        ${time.get('month')}`)
    log(`time.get('date'):         ${time.get('date')}`)
    log(`time.get('day'):          ${time.get('day')}`)
    log(`time.get('hour'):         ${time.get('hour')}`)
    log(`time.get('minute'):       ${time.get('minute')}`)
    log(`time.get('second'):       ${time.get('second')}`)
    log(`time.get('millisecond'):  ${time.get('millisecond')}`)

    log(`time.set('year', 2022):      ${time.set('year', 2022)}`)
    log(`time.set('month', 0):        ${time.set('month', 0)}`)
    log(`time.set('date', 13):        ${time.set('date', 13)}`)
    log(`time.set('day', 1):          ${time.set('day', 1)}`)
    log(`time.set('hour', 1):         ${time.set('hour', 1)}`)
    log(`time.set('minute', 3):       ${time.set('minute', 3)}`)
    log(`time.set('second', 5):       ${time.set('second', 5)}`)
    log(`time.set('millisecond', 7):  ${time.set('millisecond', 7)}`)
  })
})

• 输出

moment.js getter/setter
  second
    time:              Mon Nov 01 2021 23:59:59 GMT+0800
    time.second():     59
    time.second(996):  Mon Nov 01 2021 23:59:30 GMT+0800
    time.second():     30
  hour
    time:          Mon Nov 01 2021 23:59:30 GMT+0800
    time.hour():   23
    time.hour(1):  Mon Nov 01 2021 01:59:30 GMT+0800
    time.hour():   1
  get/set
    current time:             Mon Nov 01 2021 23:59:59 GMT+0800
    time.get('year'):         2021
    time.get('month'):        10
    time.get('date'):         1
    time.get('day'):          1
    time.get('hour'):         23
    time.get('minute'):       59
    time.get('second'):       59
    time.get('millisecond'):  699
    time.set('year', 2022):      Tue Nov 01 2022 23:59:59 GMT+0800
    time.set('month', 0):        Sat Jan 01 2022 23:59:59 GMT+0800
    time.set('date', 13):        Thu Jan 13 2022 23:59:59 GMT+0800
    time.set('day', 1):          Mon Jan 10 2022 23:59:59 GMT+0800
    time.set('hour', 1):         Mon Jan 10 2022 01:59:59 GMT+0800
    time.set('minute', 3):       Mon Jan 10 2022 01:03:59 GMT+0800
    time.set('second', 5):       Mon Jan 10 2022 01:03:05 GMT+0800
    time.set('millisecond', 7):  Mon Jan 10 2022 01:03:05 GMT+0800

1.3 日期操作(加、减、对齐、选择)

第三个场景我们可能会需要对当前的时间对象进行加法、减法的操作，或是向某个时间单位的头尾进行对齐，以及多个时间单位选择最早/最晚的时间，可用的函数标签如下

moment#add(val, unit)       // 在 unit 单位加上 val 值
moment#subtract(val, unit)  // 在 unit 单位减去 val 值
moment#startOf(unit)  // 向下取整到最近的 unit 单位
moment#endOf(unit)    // 向上取整到最近的 unit 单位
moment.max(...values)  // 取参数中最大(最晚)的时间
moment.min(...values)  // 取参数中最小(最早)的时间

• src/moment/3_operate.js

const moment = require('moment')
const { log, group } = require('../utils/group')

group('moment.js operate', () => {
  const origin = moment('2019-11-01 23:59:59.699')

  let time = origin.clone()
  group('add', () => {
    log(`current time:            ${time}`)
    log(`time.add(365, 'days'):   ${time.add(365, 'days')}`)
    log(`reset time:              ${time.set('year', 2019)}`)
    log(`time.add(1, 'years'):    ${time.add(1, 'years')}`)
    log(`time.add(8, 'd'):        ${time.add(8, 'd')}`)
    log(`time.add({ days: 7 }):   ${time.add({ days: 7 })}`)
  })

  time = origin.clone().year(2020)
  group('subtract', () => {
    log(`current time:                ${time}`)
    log(`time.subtract(365, 'days'):  ${time.subtract(365, 'days')}`)
    log(`reset time:                  ${time.year(2020).date(1)}`)
    log(`time.subtract(1, 'years'):   ${time.subtract(1, 'years')}`)
  })

  group('startOf/endOf', () => {
    time = moment('2019-01-01 01:30:30.333')
    log(`time:                    ${time}`)
    log(`time.startOf('minute'):  ${time.clone().startOf('minute')}`)
    log(`time.startOf('hour'):    ${time.clone().startOf('hour')}`)

    log(`time:                  ${time}`)
    log(`time.endOf('minute'):  ${time.clone().endOf('minute')}`)
    log(`time.endOf('hour'):    ${time.clone().endOf('hour')}`)
  })

  group('max/min', () => {
    const laterOne = moment('2020-01-01 12')
    const earlyOne = moment('2020-01-01 05')
    log(`earlyOne:                                     ${earlyOne}`)
    log(`laterOne:                                     ${laterOne}`)

    log(`moment.max(earlyOne, laterOne):               ${moment.max(earlyOne, laterOne)}`)
    log(`moment.max(earlyOne, laterOne) === laterOne:  ${moment.max(earlyOne, laterOne) === laterOne}`)

    log(`moment.min(earlyOne, laterOne):               ${moment.min(earlyOne, laterOne)}`)
    log(`moment.min(earlyOne, laterOne) === earlyOne:  ${moment.min(earlyOne, laterOne) === earlyOne}`)
  })
})

• 输出

moment.js operate
  add
    current time:            Fri Nov 01 2019 23:59:59 GMT+0800
    time.add(365, 'days'):   Sat Oct 31 2020 23:59:59 GMT+0800
    reset time:              Thu Oct 31 2019 23:59:59 GMT+0800
    time.add(1, 'years'):    Sat Oct 31 2020 23:59:59 GMT+0800
    time.add(8, 'd'):        Sun Nov 08 2020 23:59:59 GMT+0800
    time.add({ days: 7 }):   Sun Nov 15 2020 23:59:59 GMT+0800
  subtract
    current time:                Sun Nov 01 2020 23:59:59 GMT+0800
    time.subtract(365, 'days'):  Sat Nov 02 2019 23:59:59 GMT+0800
    reset time:                  Sun Nov 01 2020 23:59:59 GMT+0800
    time.subtract(1, 'years'):   Fri Nov 01 2019 23:59:59 GMT+0800
  startOf/endOf
    time:                    Tue Jan 01 2019 01:30:30 GMT+0800
    time.startOf('minute'):  Tue Jan 01 2019 01:30:00 GMT+0800
    time.startOf('hour'):    Tue Jan 01 2019 01:00:00 GMT+0800
    time:                  Tue Jan 01 2019 01:30:30 GMT+0800
    time.endOf('minute'):  Tue Jan 01 2019 01:30:59 GMT+0800
    time.endOf('hour'):    Tue Jan 01 2019 01:59:59 GMT+0800
  max/min
    earlyOne:                                     Wed Jan 01 2020 05:00:00 GMT+0800
    laterOne:                                     Wed Jan 01 2020 12:00:00 GMT+0800
    moment.max(earlyOne, laterOne):               Wed Jan 01 2020 12:00:00 GMT+0800
    moment.max(earlyOne, laterOne) === laterOne:  true
    moment.min(earlyOne, laterOne):               Wed Jan 01 2020 05:00:00 GMT+0800
    moment.min(earlyOne, laterOne) === earlyOne:  true

1.4 查询(判断、比较)

第四个场景是进行时间的判断、比较，给出函数标签

moment#isBefore(other)  // 判断当前实例时间是否早于 other
moment#isSame(other)    // 判断当前实例时间是否等于 other
moment#isAfter(other)   // 判断当前实例时间是否晚于 other
moment#isBetween(from, to)   // 判断当前实例时间是否介于 from 和 to 之间
moment#isLeapYear()     // 判断是否为闰年

• src/moment/4_query.js

const moment = require('moment')
const { log, group } = require('../utils/group')

group('moment.js query', () => {
  const earlyOne = moment('2020-01-01 05')
  const laterOne = moment('2020-01-01 12')
  const middleOne = moment('2020-01-01 08')

  log(`earlyOne:   ${earlyOne}`)
  log(`laterOne:   ${laterOne}`)
  log(`middleOne:  ${middleOne}`)

  group('isBefore', () => {
    log(`earlyOne.isBefore(laterOne):  ${earlyOne.isBefore(laterOne)}`)
    log(`laterOne.isBefore(earlyOne):  ${laterOne.isBefore(earlyOne)}`)
    log(`earlyOne.isBefore(earlyOne):  ${earlyOne.isBefore(earlyOne)}`)
  })

  group('isSame', () => {
    log(`earlyOne.isSame(laterOne):  ${earlyOne.isSame(laterOne)}`)
    log(`laterOne.isSame(earlyOne):  ${laterOne.isSame(earlyOne)}`)
    log(`earlyOne.isSame(earlyOne):  ${earlyOne.isSame(earlyOne)}`)
  })

  group('isAfter', () => {
    log(`earlyOne.isAfter(laterOne):  ${earlyOne.isAfter(laterOne)}`)
    log(`laterOne.isAfter(earlyOne):  ${laterOne.isAfter(earlyOne)}`)
    log(`earlyOne.isAfter(earlyOne):  ${earlyOne.isAfter(earlyOne)}`)
  })

  group('isBetween', () => {
    log(`middleOne.isBetween(earlyOne, laterOne):  ${middleOne.isBetween(earlyOne, laterOne)}`)
    log(`middleOne.isBetween(laterOne, earlyOne):  ${middleOne.isBetween(laterOne, earlyOne)}`)
  })

  group('isLeapYear', () => {
    log(`moment('1600').isLeapYear():  ${moment('1600').isLeapYear()}`)
    log(`moment('1800').isLeapYear():  ${moment('1800').isLeapYear()}`)
    log(`moment('2000').isLeapYear():  ${moment('2000').isLeapYear()}`)
    log(`moment('2020').isLeapYear():  ${moment('2020').isLeapYear()}`)
  })
})

• 输出

moment.js query
  earlyOne:   Wed Jan 01 2020 05:00:00 GMT+0800
  laterOne:   Wed Jan 01 2020 12:00:00 GMT+0800
  middleOne:  Wed Jan 01 2020 08:00:00 GMT+0800
  isBefore
    earlyOne.isBefore(laterOne):  true
    laterOne.isBefore(earlyOne):  false
    earlyOne.isBefore(earlyOne):  false
  isSame
    earlyOne.isSame(laterOne):  false
    laterOne.isSame(earlyOne):  false
    earlyOne.isSame(earlyOne):  true
  isAfter
    earlyOne.isAfter(laterOne):  false
    laterOne.isAfter(earlyOne):  true
    earlyOne.isAfter(earlyOne):  false
  isBetween
    middleOne.isBetween(earlyOne, laterOne):  true
    middleOne.isBetween(laterOne, earlyOne):  false
  isLeapYear
    moment('1600').isLeapYear():  true
    moment('1800').isLeapYear():  false
    moment('2000').isLeapYear():  true
    moment('2020').isLeapYear():  true

1.5 格式化输出

最后一个是时间的格式化输出，是我们可以直接透过口令(模版)来进行字符串格式化输出，而不再需要自己组合时间对象的属性

moment#format(template)  // 根据模版(口令)进行格式化并返回字符串
moment#from(other)  // 输出自 other 到当前实例的语义化时间间隔
moment#diff(other)  // 比较与 other 相差的时间，返回时间戳
moment#unix()       // 当前时间的 unix 时间戳(单位：秒)
moment#valueOf()    // 当前时间的时间戳(单位：毫秒)

• src/moment/5_format.js

const moment = require('moment')
const { log, group } = require('../utils/group')

group('moment.js format', () => {
  let earlyTime = moment([2020, 1, 1])
  const origin = moment()
  let time = origin.clone()

  log(`earlyTime:  ${earlyTime}`)
  log(`time:       ${time}`)

  group('format', () => {
    log(`time.format():                       ${time.format()}`)
    log(`time.format('YYYY-MM-DD'):           ${time.format('YYYY-MM-DD')}`)
    log(`time.format('YYYY.MM.DD HH:mm:ss'):  ${time.format('YYYY.MM.DD HH:mm:ss')}`)
  })

  group('from', () => {
    log(`time.from(earlyTime):        ${time.from(earlyTime)}`)
    log(`time.from(earlyTime, true):  ${time.from(earlyTime, true)}`)
  })

  group('diff', () => {
    log(`time.subtract(earlyTime).valueOf():  ${time.subtract(earlyTime).valueOf()}`)
    time = origin.clone()
    log(`time.diff(earlyTime):                ${time.diff(earlyTime)}`)
    log(`typeof time.subtract(earlyTime):     ${typeof time.subtract(earlyTime)}`)
    log(`typeof time.diff(earlyTime):         ${typeof time.diff(earlyTime)}`)
  })

  group('unix/valueOf', () => {
    time = origin.clone()
    log(`time.subtract(earlyTime).unix():     ${time.subtract(earlyTime).unix()}`)
    time = origin.clone()
    log(`time.subtract(earlyTime).valueOf():  ${time.subtract(earlyTime).valueOf()}`)
  })
})

• 输出

moment.js format
  earlyTime:  Sat Feb 01 2020 00:00:00 GMT+0800
  time:       Fri May 21 2021 14:37:10 GMT+0800
  format
    time.format():                       2021-05-21T14:37:10+08:00
    time.format('YYYY-MM-DD'):           2021-05-21
    time.format('YYYY.MM.DD HH:mm:ss'):  2021.05.21 14:37:10
  from
    time.from(earlyTime):        in a year
    time.from(earlyTime, true):  a year
  diff
    time.subtract(earlyTime).valueOf():  41092630034
    time.diff(earlyTime):                41092630034
    typeof time.subtract(earlyTime):     object
    typeof time.diff(earlyTime):         number
  unix/valueOf
    time.subtract(earlyTime).unix():     41092630
    time.subtract(earlyTime).valueOf():  41092630034
✨  Done in 0.19s.

2. Day.js

Day.js 的能力几乎与 Moment.js 一模一样，最主要的差别在于模块化方式和实现细节，下一个段落会进行单独说明。

下面我们先来看看直接从 moment 复制过来的示例代码，你会发现根本就是 99.99% 相似

2.1 创建时间日期对象

• src/dayjs/1_parse.js

const dayjs = require('dayjs')
const customParseFormat = require('dayjs/plugin/customParseFormat')
const { log, group } = require('../utils/group')

group('day.js parse', () => {
  dayjs.extend(customParseFormat)
  group('dayjs', () => {
    log(`dayjs():                            ${dayjs().format()}`)
    log(`dayjs('2021-11-01'):                ${dayjs('2021-11-01').format()}`)
    log(`dayjs('2021-11-01 23:59:59'):       ${dayjs('2021-11-01 23:59:59').format()}`)
    log(`dayjs('20211101T235959'):           ${dayjs('20211101T235959').format()}`)
    log(`dayjs('01-11-2021', 'DD-MM-YYYY'):  ${dayjs('01-11-2021', 'DD-MM-YYYY').format()}`)
  })

  group('clone', () => {
    const m1 = dayjs()
    const m2 = dayjs(m1)
    const m3 = m2.clone()
    log(`m1:  ${m1.toString()}`)
    log(`m2:  ${m2.toString()}`)
    log(`m3:  ${m3.toString()}`)
    log(`m1 === m2:                        ${m1 === m2}`)
    log(`m1 === m3:                        ${m1 === m3}`)
    log(`m2 === m3:                        ${m2 === m3}`)
    log(`m1.toString() === m2.toString():  ${m1.toString() === m2.toString()}`)
    log(`m1.toString() === m3.toString():  ${m1.toString() === m3.toString()}`)
    log(`m2.toString() === m3.toString():  ${m2.toString() === m3.toString()}`)
  })
})

• 输出

day.js parse
  dayjs
    dayjs():                            2021-05-21T15:44:40+08:00
    dayjs('2021-11-01'):                2021-11-01T00:00:00+08:00
    dayjs('2021-11-01 23:59:59'):       2021-11-01T23:59:59+08:00
    dayjs('20211101T235959'):           2021-11-01T23:59:59+08:00
    dayjs('01-11-2021', 'DD-MM-YYYY'):  2021-11-01T00:00:00+08:00
  clone
    m1:  Fri, 21 May 2021 07:44:40 GMT
    m2:  Fri, 21 May 2021 07:44:40 GMT
    m3:  Fri, 21 May 2021 07:44:40 GMT
    m1 === m2:                        false
    m1 === m3:                        false
    m2 === m3:                        false
    m1.toString() === m2.toString():  true
    m1.toString() === m3.toString():  true
    m2.toString() === m3.toString():  true

2.1.1 差异

我们可以看到差别在于从 moment 函数变成使用 dayjs 函数，同时不能使用数组来描述时间，这个倒是比较好解决

同时对于格式化输出的能力，我们需要透过插件(Plugin)的方式来引入

const customParseFormat = require('dayjs/plugin/customParseFormat')

dayjs.extend(customParseFormat)

2.2 获取/设置属性

• src/dayjs/2_get_set.js

const dayjs = require('dayjs')
const { log, group } = require('../utils/group')

group('day.js get/set', () => {
  const origin = dayjs('2021-11-01 23:59:59.699')

  let time = origin.clone()

  group('second', () => {
    log(`time:              ${time}`)
    log(`time.second():     ${time.second()}`)
    log(`time.second(996):  ${time.second(30)}`)
    log(`time.second():     ${time.second()}`)
  })

  group('hour', () => {
    log(`time:          ${time}`)
    log(`time.hour():   ${time.hour()}`)
    log(`time.hour(1):  ${time.hour(1)}`)
    log(`time.hour():   ${time.hour()}`)
  })

  time = origin.clone()

  group('get/set', () => {
    log(`current time:             ${time}`)
    log(`time.get('year'):         ${time.get('year')}`)
    log(`time.get('month'):        ${time.get('month')}`)
    log(`time.get('date'):         ${time.get('date')}`)
    log(`time.get('day'):          ${time.get('day')}`)
    log(`time.get('hour'):         ${time.get('hour')}`)
    log(`time.get('minute'):       ${time.get('minute')}`)
    log(`time.get('second'):       ${time.get('second')}`)
    log(`time.get('millisecond'):  ${time.get('millisecond')}`)

    log(`time.set('year', 2022):      ${time = time.set('year', 2022)}`)
    log(`time.set('month', 0):        ${time = time.set('month', 0)}`)
    log(`time.set('date', 13):        ${time = time.set('date', 13)}`)
    log(`time.set('day', 1):          ${time = time.set('day', 1)}`)
    log(`time.set('hour', 1):         ${time = time.set('hour', 1)}`)
    log(`time.set('minute', 3):       ${time = time.set('minute', 3)}`)
    log(`time.set('second', 5):       ${time = time.set('second', 5)}`)
    log(`time.set('millisecond', 7):  ${time = time.set('millisecond', 7)}`)
  })
})

• 输出

day.js get/set
  second
    time:              Mon, 01 Nov 2021 15:59:59 GMT
    time.second():     59
    time.second(996):  Mon, 01 Nov 2021 15:59:30 GMT
    time.second():     59
  hour
    time:          Mon, 01 Nov 2021 15:59:59 GMT
    time.hour():   23
    time.hour(1):  Sun, 31 Oct 2021 17:59:59 GMT
    time.hour():   23
  get/set
    current time:             Mon, 01 Nov 2021 15:59:59 GMT
    time.get('year'):         2021
    time.get('month'):        10
    time.get('date'):         1
    time.get('day'):          1
    time.get('hour'):         23
    time.get('minute'):       59
    time.get('second'):       59
    time.get('millisecond'):  699
    time.set('year', 2022):      Tue, 01 Nov 2022 15:59:59 GMT
    time.set('month', 0):        Sat, 01 Jan 2022 15:59:59 GMT
    time.set('date', 13):        Thu, 13 Jan 2022 15:59:59 GMT
    time.set('day', 1):          Mon, 10 Jan 2022 15:59:59 GMT
    time.set('hour', 1):         Sun, 09 Jan 2022 17:59:59 GMT
    time.set('minute', 3):       Sun, 09 Jan 2022 17:03:59 GMT
    time.set('second', 5):       Sun, 09 Jan 2022 17:03:05 GMT
    time.set('millisecond', 7):  Sun, 09 Jan 2022 17:03:05 GMT

2.2.1 差异

get/set 操作方法则一模一样，不同的是在 dayjs 里面的时间对象是一个不可改变，任何操作都会返回一个新的对象，而通常这也是比较好的表现，这便是比较需要注意的

2.3 日期操作(加、减、对齐、选择)

• src/dayjs/3_operate.js

const dayjs = require('dayjs')
const { log, group } = require('../utils/group')
const minMax = require('dayjs/plugin/minMax')

dayjs.extend(minMax)

group('day.js operate', () => {
  const origin = dayjs('2019-11-01 23:59:59.699')

  let time = origin.clone()
  group('add', () => {
    log(`current time:            ${time}`)
    log(`time.add(365, 'days'):   ${time.add(365, 'days')}`)
    log(`time.add(1, 'years'):    ${time.add(1, 'years')}`)
    log(`time.add(8, 'd'):        ${time.add(8, 'd')}`)
    log(`time.add({ days: 7 }):   ${time.add({ days: 7 })}`)
  })

  time = origin.clone().year(2020)
  group('subtract', () => {
    log(`current time:                ${time}`)
    log(`time.subtract(365, 'days'):  ${time.subtract(365, 'days')}`)
    log(`time.subtract(1, 'years'):   ${time.subtract(1, 'years')}`)
  })

  group('startOf/endOf', () => {
    time = dayjs('2019-01-01 01:30:30.333')
    log(`time:                    ${time}`)
    log(`time.startOf('minute'):  ${time.clone().startOf('minute')}`)
    log(`time.startOf('hour'):    ${time.clone().startOf('hour')}`)

    log(`time:                  ${time}`)
    log(`time.endOf('minute'):  ${time.clone().endOf('minute')}`)
    log(`time.endOf('hour'):    ${time.clone().endOf('hour')}`)
  })

  group('max/min', () => {
    const laterOne = dayjs('2020-01-01 12')
    const earlyOne = dayjs('2020-01-01 05')
    log(`earlyOne:                                    ${earlyOne}`)
    log(`laterOne:                                    ${laterOne}`)

    log(`dayjs.max(earlyOne, laterOne):               ${dayjs.max(earlyOne, laterOne)}`)
    log(`dayjs.max(earlyOne, laterOne) === laterOne:  ${dayjs.max(earlyOne, laterOne) === laterOne}`)

    log(`dayjs.min(earlyOne, laterOne):               ${dayjs.min(earlyOne, laterOne)}`)
    log(`dayjs.min(earlyOne, laterOne) === earlyOne:  ${dayjs.min(earlyOne, laterOne) === earlyOne}`)
  })

})

• 输出

day.js operate
  add
    current time:            Fri, 01 Nov 2019 15:59:59 GMT
    time.add(365, 'days'):   Sat, 31 Oct 2020 15:59:59 GMT
    time.add(1, 'years'):    Sun, 01 Nov 2020 15:59:59 GMT
    time.add(8, 'd'):        Sat, 09 Nov 2019 15:59:59 GMT
    time.add({ days: 7 }):   Invalid Date
  subtract
    current time:                Sun, 01 Nov 2020 15:59:59 GMT
    time.subtract(365, 'days'):  Sat, 02 Nov 2019 15:59:59 GMT
    time.subtract(1, 'years'):   Fri, 01 Nov 2019 15:59:59 GMT
  startOf/endOf
    time:                    Mon, 31 Dec 2018 17:30:30 GMT
    time.startOf('minute'):  Mon, 31 Dec 2018 17:30:00 GMT
    time.startOf('hour'):    Mon, 31 Dec 2018 17:00:00 GMT
    time:                  Mon, 31 Dec 2018 17:30:30 GMT
    time.endOf('minute'):  Mon, 31 Dec 2018 17:30:59 GMT
    time.endOf('hour'):    Mon, 31 Dec 2018 17:59:59 GMT
  max/min
    earlyOne:                                    Tue, 31 Dec 2019 21:00:00 GMT
    laterOne:                                    Wed, 01 Jan 2020 04:00:00 GMT
    dayjs.max(earlyOne, laterOne):               Wed, 01 Jan 2020 04:00:00 GMT
    dayjs.max(earlyOne, laterOne) === laterOne:  true
    dayjs.min(earlyOne, laterOne):               Tue, 31 Dec 2019 21:00:00 GMT
    dayjs.min(earlyOne, laterOne) === earlyOne:  true

2.3.1 差异

第三个对于时间类型的操作也是近乎一致；不同的是比大小的 min/max 方法一样要透过插件的形式来引入

const minMax = require('dayjs/plugin/minMax')

dayjs.extend(minMax)

2.4 查询(判断、比较)

• src/dayjs/4_query.js

const dayjs = require('dayjs')
const { log, group } = require('../utils/group')
const isBetween = require('dayjs/plugin/isBetween')
const isLeapYear = require('dayjs/plugin/isLeapYear')

dayjs.extend(isBetween)
dayjs.extend(isLeapYear)

group('day.js query', () => {
  const earlyOne = dayjs('2020-01-01 05')
  const laterOne = dayjs('2020-01-01 12')
  const middleOne = dayjs('2020-01-01 08')

  log(`earlyOne:   ${earlyOne}`)
  log(`laterOne:   ${laterOne}`)
  log(`middleOne:  ${middleOne}`)

  group('isBefore', () => {
    log(`earlyOne.isBefore(laterOne):  ${earlyOne.isBefore(laterOne)}`)
    log(`laterOne.isBefore(earlyOne):  ${laterOne.isBefore(earlyOne)}`)
    log(`earlyOne.isBefore(earlyOne):  ${earlyOne.isBefore(earlyOne)}`)
  })

  group('isSame', () => {
    log(`earlyOne.isSame(laterOne):  ${earlyOne.isSame(laterOne)}`)
    log(`laterOne.isSame(earlyOne):  ${laterOne.isSame(earlyOne)}`)
    log(`earlyOne.isSame(earlyOne):  ${earlyOne.isSame(earlyOne)}`)
  })

  group('isAfter', () => {
    log(`earlyOne.isAfter(laterOne):  ${earlyOne.isAfter(laterOne)}`)
    log(`laterOne.isAfter(earlyOne):  ${laterOne.isAfter(earlyOne)}`)
    log(`earlyOne.isAfter(earlyOne):  ${earlyOne.isAfter(earlyOne)}`)
  })

  group('isBetween', () => {
    log(`middleOne.isBetween(earlyOne, laterOne):  ${middleOne.isBetween(earlyOne, laterOne)}`)
    log(`middleOne.isBetween(laterOne, earlyOne):  ${middleOne.isBetween(laterOne, earlyOne)}`)
  })

  group('isLeapYear', () => {
    log(`moment('1600').isLeapYear():  ${dayjs('1600').isLeapYear()}`)
    log(`moment('1800').isLeapYear():  ${dayjs('1800').isLeapYear()}`)
    log(`moment('2000').isLeapYear():  ${dayjs('2000').isLeapYear()}`)
    log(`moment('2020').isLeapYear():  ${dayjs('2020').isLeapYear()}`)
  })
})

• 输出

day.js query
  earlyOne:   Tue, 31 Dec 2019 21:00:00 GMT
  laterOne:   Wed, 01 Jan 2020 04:00:00 GMT
  middleOne:  Wed, 01 Jan 2020 00:00:00 GMT
  isBefore
    earlyOne.isBefore(laterOne):  true
    laterOne.isBefore(earlyOne):  false
    earlyOne.isBefore(earlyOne):  false
  isSame
    earlyOne.isSame(laterOne):  false
    laterOne.isSame(earlyOne):  false
    earlyOne.isSame(earlyOne):  true
  isAfter
    earlyOne.isAfter(laterOne):  false
    laterOne.isAfter(earlyOne):  true
    earlyOne.isAfter(earlyOne):  false
  isBetween
    middleOne.isBetween(earlyOne, laterOne):  true
    middleOne.isBetween(laterOne, earlyOne):  true
  isLeapYear
    dayjs('1600').isLeapYear():  true
    dayjs('1800').isLeapYear():  false
    dayjs('2000').isLeapYear():  true
    dayjs('2020').isLeapYear():  true

2.4.1 差异

同样的 isBetween, isLeapYear 需要使用插件引入

const isBetween = require('dayjs/plugin/isBetween')
const isLeapYear = require('dayjs/plugin/isLeapYear')

dayjs.extend(isBetween)
dayjs.extend(isLeapYear)

2.5 格式化输出

• src/dayjs/5_format.js

const dayjs = require('dayjs')
const { log, group } = require('../utils/group')
const relativeTime = require('dayjs/plugin/relativeTime')

dayjs.extend(relativeTime)

group('day.js format', () => {
  let earlyTime = dayjs([2020, 1, 1])
  const origin = dayjs()
  let time = origin.clone()

  log(`earlyTime:  ${earlyTime}`)
  log(`time:       ${time}`)

  group('format', () => {
    log(`time.format():                       ${time.format()}`)
    log(`time.format('YYYY-MM-DD'):           ${time.format('YYYY-MM-DD')}`)
    log(`time.format('YYYY.MM.DD HH:mm:ss'):  ${time.format('YYYY.MM.DD HH:mm:ss')}`)
  })

  group('from', () => {
    log(`time.from(earlyTime):        ${time.from(earlyTime)}`)
    log(`time.from(earlyTime, true):  ${time.from(earlyTime, true)}`)
  })

  group('diff', () => {
    log(`time.subtract(earlyTime).valueOf():  ${time.subtract(earlyTime).valueOf()}`)
    time = origin.clone()
    log(`time.diff(earlyTime):                ${time.diff(earlyTime)}`)
    log(`typeof time.subtract(earlyTime):     ${typeof time.subtract(earlyTime)}`)
    log(`typeof time.diff(earlyTime):         ${typeof time.diff(earlyTime)}`)
  })

  group('unix/valueOf', () => {
    time = origin.clone()
    log(`time.subtract(earlyTime).unix():     ${time.subtract(earlyTime).unix()}`)
    time = origin.clone()
    log(`time.subtract(earlyTime).valueOf():  ${time.subtract(earlyTime).valueOf()}`)
  })
})

• 输出

day.js format
  earlyTime:  Tue, 31 Dec 2019 16:00:00 GMT
  time:       Fri, 21 May 2021 07:44:40 GMT
  format
    time.format():                       2021-05-21T15:44:40+08:00
    time.format('YYYY-MM-DD'):           2021-05-21
    time.format('YYYY.MM.DD HH:mm:ss'):  2021.05.21 15:44:40
  from
    time.from(earlyTime):        in a year
    time.from(earlyTime, true):  a year
  diff
    time.subtract(earlyTime).valueOf():  43775080504
    time.diff(earlyTime):                43775080504
    typeof time.subtract(earlyTime):     object
    typeof time.diff(earlyTime):         number
  unix/valueOf
    time.subtract(earlyTime).unix():     43775080
    time.subtract(earlyTime).valueOf():  43775080504
✨  Done in 0.24s.

2.5.1 差异

from 方法或其他相对时间的相关方法则需要使用 relativeTime 引入

const relativeTime = require('dayjs/plugin/relativeTime')

dayjs.extend(relativeTime)

3. Day.js 相较于 Moment.js 的好处

接下来比较重要的是来说明一下为什么说用 Day.js 比 moment.js 好，首先我们先来说说 moment.js

moment.js 算是比较早期，同时经过多次版本的更新，不断有新功能被添加到整个 moment 对象上，当所有功能、特性都聚集在这一个 moment 对象的时候就显得异常臃肿，同时也代表着所有代码都关联在一起。而且很重要的一点是 moment.js 对于原生 Date 对象存在侵入性的修改，与 day.js 全部都迁移到自己的 dayjs 对象内部不同。

3.1 Moment.js 的问题

也就是说当我们使用 moment.js 的时候会存在以下问题：

1. 类库中代码非常 臃肿，携带非常多没有被使用到的多余代码
2. 多余的特性、检查，使得因为一些没有被使用的特性，却总是需要在运行时花费额外开销来处理特性分类的问题
3. moment.js 自己的作者也声明由于 moment 对象已经变得过于臃肿，所以已经停止进行新版本新特性的更新，进入 维护期；同时作者也推荐使用其他更新的库如 Day.js，或是未来的新标准 Intl 对象的使用

3.2 Day.js 的好处

使用 Day.js 则会为我们带来以下好处

1. Day.js 的 API 几乎与 Moment.js 有 9 成以上相似，所以在进行迁移的时候的学习成本极低

2. Day.js 将不同的特性分成各个插件(Plugin)，使用者可以根据需要主动引入并对全局对象进行扩展

   const xxx = require('dayjs/plugin/xxx')
   
   dayjs.extend(xxx)
   

   这对于我们来说不仅是代码上的鲁棒性更高，同时减少 dayjs 对象的复杂度和大小。同时这对于我们的项目进行打包的时候也有助于打包工具的 tree-shaking 可以显著的降低无用代码和无用特性的引入。

结语

本篇提供了两个日期时间库使用时的大量示例，供大家参考和查阅，更详细更精确的 API 使用推荐大家去看类库的官方文档边查边用更对味。

其他资源

参考连接

Title	Link
moment.js	http://momentjs.cn/
day.js	https://dayjs.fenxianglu.cn/
时间标准基础知识UTC和ISO8601	https://www.cnblogs.com/doit8791/p/10398997.html
Moment.js官方推荐使用其它时间处理库代替	https://www.w3cschool.cn/article/b0266c23d158f0.html

阅读笔记参考

https://github.com/superfreeeee/Blog-code/tree/main/front_end/others/moment-dayjs