parseISOString.js

parseISOString.js

/**
 * Parse an ISO string with or without an offset
 *   e.g. '2014-04-02T20:00:00-0600'
 *        '2014-04-02T20:00:00Z'
 *        '2014-02'
 *
 * Allows decimal seconds if supplied
 *   e.g. '2014-04-02T20:00:00.123-0600'
 *
 * If no offset is supplied (or it's Z), treat as UTC (per ECMA-262)
 *
 * If date only, e.g. '2014-04-02' or '2014-02', treat as UTC date (per ECMA-262)
 * All parts after year are optional
 * Don't allow two digit years to be converted to 20th century years
 * @param {string} s - ISO 860 date string
*/
function parseISOString(s) {
  var invalidDate = new Date(NaN);
  var t = s.split(/\D+/g);
  var hasOffset = /[-+]\d{4}$/.test(s);

  // Whether decimal seconds are present changes the offset field and ms value
  var hasDecimalSeconds = /[T ]\d{2}:\d{2}:\d{2}\.\d+/i.test(s);
  var offset = hasDecimalSeconds? t[7] : t[6];
  var offSign;
  var yr  = +t[0],
      mo  = t[1]? --t[1] : 0,
      da  = +t[2] || 1,
      hr  = +t[3] || 0,
      min = +t[4] || 0,
      sec = +t[5] || 0,
      ms  = hasDecimalSeconds? +t[6] : 0,
      offSign = hasOffset? /-\d{4}$/.test(s)? 1 : -1 : 0,
      offHr   = hasOffset? offset/100 | 0 : 0,
      offMin  = hasOffset? offset%100 : 0;

  // Ensure time values are in range, otherwise invalid date.
  // Values can't be -ve as splitting on non-digit character
  if (hr > 24 || min > 59 || sec > 59 || ms > 1000 || offHr > 24 || offMin > 59){
    return invalidDate;
  }

  // Create a date object from date parts, check for validity
  // Avoid two digit years being converted to 20th century
  var d = new Date();
  d.setUTCFullYear(yr, mo, da);

  // Check that date values are valid
  if (d.getUTCFullYear() != yr || d.getUTCDate() != da) {
    return invalidDate;
  }

  // If there's an offset, apply it to minutes to get a UTC time value
  min = hasOffset? +min + offSign * (offHr * 60 + offMin) : min;

  // Set UTC time values of d
  d.setUTCHours(hr, min, sec, ms);

  return d;
}