PHP's strftime in JavaScript

How to use

You you can install via yarn add locutus and require this function via const strftime = require('locutus/php/datetime/strftime').

It is important to use a bundler that supports tree-shaking so that you only ship the functions that you actually use to your browser, instead of all of Locutus, which is massive. Examples are: Parcel, webpack, or rollup.js. For server-side use this is typically less of a concern.

Examples

Please note that these examples are distilled from test cases that automatically verify our functions still work correctly. This could explain some quirky ones.

#	code	expected result
1	strftime("%A", 1062462400); // Return value will depend on date and locale	'Tuesday'
2	strftime('%F', 1577836800);	'2020-01-01'
3	(() => {let e = process.env, tz = e.TZ; e.TZ = 'Europe/Vienna'; let r = strftime('%j', 1680307200); e.TZ = tz; return r;})();	'091'

Notes

• Uses global: locutus to store locale info

Here’s what our current JavaScript equivalent to PHP's strftime looks like.

module.exports = function strftime(fmt, timestamp) {
  //       discuss at: https://locutus.io/php/strftime/
  //      original by: Blues (https://tech.bluesmoon.info/)
  // reimplemented by: Brett Zamir (https://brett-zamir.me)
  //         input by: Alex
  //      bugfixed by: Brett Zamir (https://brett-zamir.me)
  //      improved by: Brett Zamir (https://brett-zamir.me)
  //           note 1: Uses global: locutus to store locale info
  //        example 1: strftime("%A", 1062462400); // Return value will depend on date and locale
  //        returns 1: 'Tuesday'
  //      bugfixed by: Markus Marchewa
  //        example 2: strftime('%F', 1577836800);
  //        returns 2: '2020-01-01'
  //        example 3: (() => {let e = process.env, tz = e.TZ; e.TZ = 'Europe/Vienna'; let r = strftime('%j', 1680307200); e.TZ = tz; return r;})();
  //        returns 3: '091'

  const setlocale = require('../strings/setlocale')

  const $global = typeof window !== 'undefined' ? window : global
  $global.$locutus = $global.$locutus || {}
  const $locutus = $global.$locutus

  // ensure setup of localization variables takes place
  setlocale('LC_ALL', 0)

  const _xPad = function (x, pad, r) {
    if (typeof r === 'undefined') {
      r = 10
    }
    for (; parseInt(x, 10) < r && r > 1; r /= 10) {
      x = pad.toString() + x
    }
    return x.toString()
  }

  const locale = $locutus.php.localeCategories.LC_TIME
  const lcTime = $locutus.php.locales[locale].LC_TIME

  var _formats = {
    a: function (d) {
      return lcTime.a[d.getDay()]
    },
    A: function (d) {
      return lcTime.A[d.getDay()]
    },
    b: function (d) {
      return lcTime.b[d.getMonth()]
    },
    B: function (d) {
      return lcTime.B[d.getMonth()]
    },
    C: function (d) {
      return _xPad(parseInt(d.getFullYear() / 100, 10), 0)
    },
    d: ['getDate', '0'],
    e: ['getDate', ' '],
    g: function (d) {
      return _xPad(parseInt(this.G(d) / 100, 10), 0)
    },
    G: function (d) {
      let y = d.getFullYear()
      const V = parseInt(_formats.V(d), 10)
      const W = parseInt(_formats.W(d), 10)

      if (W > V) {
        y++
      } else if (W === 0 && V >= 52) {
        y--
      }

      return y
    },
    H: ['getHours', '0'],
    I: function (d) {
      const I = d.getHours() % 12
      return _xPad(I === 0 ? 12 : I, 0)
    },
    j: function (d) {
      // calculate the difference between the given date and the start of the year (in localtime), DST shifts may lead
      // to deltas less than multiples of 24 hours (the day when DST starts has just 23 hours), compensate by adding
      // the difference between timezone offsets (subtract since values are negative for positive offsets), e.g.:
      // 2020-05-01 00:00:00 CEST, timezone +0200, offset -120
      // 2020-01-01 00:00:00 CET , timezone +0100, offset  -60
      const b = new Date(d.getFullYear(), 0)
      const ms = d - b - (d.getTimezoneOffset() - b.getTimezoneOffset()) * 60000
      const doy = parseInt(ms / 60000 / 60 / 24, 10) + 1
      return _xPad(doy, 0, 100)
    },
    k: ['getHours', '0'],
    // not in PHP, but implemented here (as in Yahoo)
    l: function (d) {
      const l = d.getHours() % 12
      return _xPad(l === 0 ? 12 : l, ' ')
    },
    m: function (d) {
      return _xPad(d.getMonth() + 1, 0)
    },
    M: ['getMinutes', '0'],
    p: function (d) {
      return lcTime.p[d.getHours() >= 12 ? 1 : 0]
    },
    P: function (d) {
      return lcTime.P[d.getHours() >= 12 ? 1 : 0]
    },
    s: function (d) {
      // Yahoo uses return parseInt(d.getTime()/1000, 10);
      return Date.parse(d) / 1000
    },
    S: ['getSeconds', '0'],
    u: function (d) {
      const dow = d.getDay()
      return dow === 0 ? 7 : dow
    },
    U: function (d) {
      const doy = parseInt(_formats.j(d), 10)
      const rdow = 6 - d.getDay()
      const woy = parseInt((doy + rdow) / 7, 10)
      return _xPad(woy, 0)
    },
    V: function (d) {
      const woy = parseInt(_formats.W(d), 10)
      const dow11 = new Date('' + d.getFullYear() + '/1/1').getDay()
      // First week is 01 and not 00 as in the case of %U and %W,
      // so we add 1 to the final result except if day 1 of the year
      // is a Monday (then %W returns 01).
      // We also need to subtract 1 if the day 1 of the year is
      // Friday-Sunday, so the resulting equation becomes:
      let idow = woy + (dow11 > 4 || dow11 <= 1 ? 0 : 1)
      if (idow === 53 && new Date('' + d.getFullYear() + '/12/31').getDay() < 4) {
        idow = 1
      } else if (idow === 0) {
        idow = _formats.V(new Date('' + (d.getFullYear() - 1) + '/12/31'))
      }
      return _xPad(idow, 0)
    },
    w: 'getDay',
    W: function (d) {
      const doy = parseInt(_formats.j(d), 10)
      const rdow = 7 - _formats.u(d)
      const woy = parseInt((doy + rdow) / 7, 10)
      return _xPad(woy, 0, 10)
    },
    y: function (d) {
      return _xPad(d.getFullYear() % 100, 0)
    },
    Y: 'getFullYear',
    z: function (d) {
      const o = d.getTimezoneOffset()
      const H = _xPad(parseInt(Math.abs(o / 60), 10), 0)
      const M = _xPad(o % 60, 0)
      return (o > 0 ? '-' : '+') + H + M
    },
    Z: function (d) {
      return d.toString().replace(/^.*\(([^)]+)\)$/, '$1')
    },
    '%': function (d) {
      return '%'
    },
  }

  const _date =
    typeof timestamp === 'undefined'
      ? new Date()
      : timestamp instanceof Date
        ? new Date(timestamp)
        : new Date(timestamp * 1000)

  const _aggregates = {
    c: 'locale',
    D: '%m/%d/%y',
    F: '%Y-%m-%d',
    h: '%b',
    n: '\n',
    r: 'locale',
    R: '%H:%M',
    t: '\t',
    T: '%H:%M:%S',
    x: 'locale',
    X: 'locale',
  }

  // First replace aggregates (run in a loop because an agg may be made up of other aggs)
  while (fmt.match(/%[cDFhnrRtTxX]/)) {
    fmt = fmt.replace(/%([cDFhnrRtTxX])/g, function (m0, m1) {
      const f = _aggregates[m1]
      return f === 'locale' ? lcTime[m1] : f
    })
  }

  // Now replace formats - we need a closure so that the date object gets passed through
  const str = fmt.replace(/%([aAbBCdegGHIjklmMpPsSuUVwWyYzZ%])/g, function (m0, m1) {
    const f = _formats[m1]
    if (typeof f === 'string') {
      return _date[f]()
    } else if (typeof f === 'function') {
      return f(_date)
    } else if (typeof f === 'object' && typeof f[0] === 'string') {
      return _xPad(_date[f[0]](), f[1])
    } else {
      // Shouldn't reach here
      return m1
    }
  })

  return str
}

A community effort

Not unlike Wikipedia, Locutus is an ongoing community effort. Our philosophy follows The McDonald’s Theory. This means that we assimilate first iterations with imperfections, hoping for others to take issue with-and improve them. This unorthodox approach has worked very well to foster fun and fruitful collaboration, but please be reminded to use our creations at your own risk. THE SOFTWARE IS PROVIDED "AS IS" has never been more true than for Locutus.

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