Javascript Simple Date Formatter ( https://github.com/greenn-lab/nal )

nal.js

(function() {

const i18n = {
  am: '오전',
  pm: '오후',
  pattern: {
    default: 'yyyyMMddHHmmss'
  }
}

const DP = Date.prototype
const D2 = () => /\d\d/
const D12 = () => /\d\d?/

const units = {
  yyyy: [() => /\d{4}/, DP.setFullYear, DP.getFullYear],
  yy: [
    D2,
    function (v) {
      this.setFullYear(
        Math.floor(new Date().getFullYear() / 1000) * 1000 + v
      )
    },
    function () {
      return this.getFullYear().toString().substring(2)
    }
  ],
  MM: [
    D2,
    function (v) {
      this.setMonth(v - 1)
    },
    function () {
      return `0${this.getMonth() + 1}`.substr(-2)
    }
  ],
  M: [
    D12,
    function (v) {
      this.setMonth(v - 1)
    },
    function () {
      return this.getMonth() + 1
    }
  ],
  dd: [
    D2,
    DP.setDate,
    function () {
      return `0${this.getDate()}`.substr(-2)
    }
  ],
  d: [
    D12,
    DP.setDate,
    function () {
      return this.getDate()
    }
  ],
  HH: [
    D2,
    function (v) {
      this.setHours(this.getHours() + Number(v))
    },
    function () {
      return `0${this.getHours()}`.substr(-2)
    }
  ],
  H: [
    D12,
    function (v) {
      this.setHours(this.getHours() + Number(v))
    },
    function () {
      return this.getHours()
    }
  ],
  hh: [
    D2,
    function (v) {
      this.setHours(this.getHours() + Number(v))
    },
    function () {
      return `0${this.getHours() % 12 || 12}`.substr(-2)
    }
  ],
  h: [
    D12,
    function (v) {
      this.setHours(this.getHours() + Number(v))
    },
    function () {
      return this.getHours() % 12 || 12
    }
  ],
  mm: [
    D2,
    function (v) {
      this.setMinutes(this.getMinutes() + Number(v))
    },
    function () {
      return `0${this.getMinutes()}`.substr(-2)
    }
  ],
  m: [
    D12,
    function (v) {
      this.setMinutes(this.getMinutes() + Number(v))
    },
    function () {
      return this.getMinutes()
    }
  ],
  ss: [
    D2,
    function (v) {
      this.setSeconds(this.getSeconds() + Number(v))
    },
    function () {
      return `0${this.getSeconds()}`.substr(-2)
    }
  ],
  s: [
    D12,
    function (v) {
      this.setSeconds(this.getSeconds() + Number(v))
    },
    function () {
      return this.getSeconds()
    }
  ],
  SSS: [
    () => /\d{1,3}/,
    DP.setMilliseconds,
    function () {
      return `00${this.getMilliseconds()}`.substr(-3)
    }
  ],
  SS: [
    D2,
    DP.setMilliseconds,
    function () {
      return `0${this.getMilliseconds()}`.substr(-2)
    }
  ],
  S: [
    () => /\d/,
    DP.setMilliseconds,
    function () {
      return this.getMilliseconds().toString().substring(0, 1)
    }
  ],
  a: [
    () => new RegExp([i18n.am, i18n.pm].join('|')),
    function (v) {
      v = i18n.pm === v ? 12 : 0
      this.setHours(this.getHours() + v)
    },
    function () {
      return [i18n.am, i18n.pm][Math.floor(this.getHours() / 12)]
    }
  ]
}

const format = (date, pattern = i18n.pattern.default) => {
  return pattern.replace(
    new RegExp(`(${Object.keys(units).join('|')})`, 'g'),
    function (unit) {
      return units[unit][2].call(date)
    }
  )
}

const parse = (text, pattern = i18n.pattern.default) => {
  if (!text) {
    throw new Error('required text')
  }

  const date = new Date(0, 0, 1)

  const joinUnitKeys = Object.keys(units).join('|')
  const effectedRegExp = new RegExp(joinUnitKeys)

  let patternIndex = 0
  let textIndex = 0
  let matched
  while (
    (matched = effectedRegExp.exec(pattern.substring(patternIndex)))
  ) {
    const key = matched[0]
    patternIndex += matched.index + key.length

    const [unit, setter] = units[key]
    if (unit) {
      textIndex += matched.index

      const [value] = unit().exec(text.substring(textIndex)) || []

      if (value) {
        setter.call(date, value)

        textIndex += value.length
      }
    }
  }

  return date
}


Date.prototype.i18n = i18n

Date.prototype.format = function (pattern) {
  return format(this, pattern)
}

Date.of = parse

Date.parseOf = parse

})()

nal.spec.js

const nal = require('./nal')

console.log(1, Date.parseOf('>>2021-05-14 오전 11:43:14.341', '  yyyy-MM-dd a HH:mm:ss.SSS'))

console.log(2, Date.parseOf('20210514114314'))

console.log(3, Date.parseOf('20210514 114314', 'yyyyMMdd HHmmss'))

console.log(4, Date.parseOf('20210514'))

console.log(5, new Date().format('yyyy-MM-dd a hh:mm:ss.SSS'))

console.log(6, new Date().format('yy-M-d a h:m:s.S'))

console.log(7, new Date().format('yyyy년 MM월 dd일 a hh시 mm분 ss초(SSS)'))

console.log(8, new Date().format('yyyyMMddaHHmmssSSS'))

console.log(9, new Date().format())

update// use destructuring in method "parseOf"

update// unit test