strftime.js

'use strict';

var dateNames = require('date-names');

function strftime(date, format, names) {
  var timestamp = date.getTime();

  names = names || dateNames;

  return format.replace(/%([-_0]?.)/g, function(_, c) {
    var padding = null;

    if (c.length == 2) {
      switch (c[0]) {
        case '-': padding = '';  break;
        case '_': padding = ' '; break;
        case '0': padding = '0'; break;
        default: return _; // should never reach this one
      }

      c = c[1];
    }

    switch (c) {
      case 'A': return names.days[date.getDay()];
      case 'a': return names.abbreviated_days[date.getDay()];
      case 'B': return names.months[date.getMonth()];
      case 'b': return names.abbreviated_months[date.getMonth()];
      case 'C': return pad(Math.floor(date.getFullYear() / 100), padding);
      case 'D': return strftime(date, '%m/%d/%y');
      case 'd': return pad(date.getDate(), padding);
      case 'e': return date.getDate();
      case 'F': return strftime(date, '%Y-%m-%d');
      case 'H': return pad(date.getHours(), padding);
      case 'h': return names.abbreviated_months[date.getMonth()];
      case 'I': return pad(hours12(date), padding);
      case 'j': return pad(Math.ceil((date.getTime() - (new Date(date.getFullYear(), 0, 1)).getTime()) / (1000 * 60 * 60 * 24)), 3);
      case 'k': return pad(date.getHours(), padding === null ? ' ' : padding);
      case 'L': return pad(Math.floor(timestamp % 1000), 3);
      case 'l': return pad(hours12(date), padding === null ? ' ' : padding);
      case 'M': return pad(date.getMinutes(), padding);
      case 'm': return pad(date.getMonth() + 1, padding);
      case 'n': return '\n';
      case 'o': return String(date.getDate()) + ordinal(date.getDate());
      case 'P': return date.getHours() < 12 ? names.am.toLowerCase() : names.pm.toLowerCase();
      case 'p': return date.getHours() < 12 ? names.am.toUpperCase() : names.pm.toUpperCase();
      case 'R': return strftime(date, '%H:%M');
      case 'r': return strftime(date, '%I:%M:%S %p');
      case 'S': return pad(date.getSeconds(), padding);
      case 's': return Math.floor(timestamp / 1000);
      case 'T': return strftime(date, '%H:%M:%S');
      case 't': return '\t';
      case 'U': return pad(weekNumber(date, 'sunday'), padding);
      case 'u': return date.getDay() === 0 ? 7 : date.getDay();
      case 'v': return strftime(date, '%e-%b-%Y');
      case 'W': return pad(weekNumber(date, 'monday'), padding);
      case 'w': return date.getDay();
      case 'Y': return date.getFullYear();
      case 'y': var y = String(date.getFullYear()); return y.slice(y.length - 2);
      case 'Z': var tzString = date.toString().match(/\((\w+)\)/); return tzString && tzString[1] || '';
      case 'z': var off = date.getTimezoneOffset(); return (off > 0 ? '-' : '+') + pad(Math.round(Math.abs(off / 60)), 2) + ':' + pad(off % 60, 2);
      default: return c;
    }
  });
}

function pad(n, padding, length) {
  if (typeof padding === 'number') {
    length = padding;
    padding = '0';
  }

  if (padding === null) {
    padding = '0';
  }

  length = length || 2;

  var s = String(n);

  if (padding) {
    while (s.length < length) {
      s = padding + s;
    }
  }

  return s;
}

function hours12(date) {
  var hour = date.getHours();

  if (hour === 0) {
    hour = 12;
  } else if (hour > 12) {
    hour -= 12;
  }

  return hour;
}

function ordinal(n) {
  var i = n % 10, ii = n % 100;

  if ((ii >= 11 && ii <= 13) || i === 0 || i >= 4) {
    return 'th';
  }

  switch (i) {
    case 1: return 'st';
    case 2: return 'nd';
    case 3: return 'rd';
  }
}

function weekNumber(date, firstWeekday) {
  firstWeekday = firstWeekday || 'sunday';

  var wday = date.getDay();

  if (firstWeekday == 'monday') {
    if (wday === 0) { // Sunday
      wday = 6;
    } else {
      wday--;
    }
  }

  var
    firstDayOfYear = new Date(date.getFullYear(), 0, 1),
    yday = (date - firstDayOfYear) / 86400000,
    weekNum = (yday + 7 - wday) / 7;

  return Math.floor(weekNum);
}

module.exports = strftime;