read-excel-file/commonjs/xlsx/isDateFormat.js

Read `.xlsx` files in a web browser or in Node.js

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports["default"] = isDateFormatCached;
function _createForOfIteratorHelperLoose(o, allowArrayLike) { var it = typeof Symbol !== "undefined" && o[Symbol.iterator] || o["@@iterator"]; if (it) return (it = it.call(o)).next.bind(it); if (Array.isArray(o) || (it = _unsupportedIterableToArray(o)) || allowArrayLike && o && typeof o.length === "number") { if (it) o = it; var i = 0; return function () { if (i >= o.length) return { done: true }; return { done: false, value: o[i++] }; }; } throw new TypeError("Invalid attempt to iterate non-iterable instance.\nIn order to be iterable, non-array objects must have a [Symbol.iterator]() method."); }
function _unsupportedIterableToArray(o, minLen) { if (!o) return; if (typeof o === "string") return _arrayLikeToArray(o, minLen); var n = Object.prototype.toString.call(o).slice(8, -1); if (n === "Object" && o.constructor) n = o.constructor.name; if (n === "Map" || n === "Set") return Array.from(o); if (n === "Arguments" || /^(?:Ui|I)nt(?:8|16|32)(?:Clamped)?Array$/.test(n)) return _arrayLikeToArray(o, minLen); }
function _arrayLikeToArray(arr, len) { if (len == null || len > arr.length) len = arr.length; for (var i = 0, arr2 = new Array(len); i < len; i++) arr2[i] = arr[i]; return arr2; }
// On some date formats, there's a "[$-...]" prefix that locks the locale
// to be a specific one when formatting a date using this format.
//
// https://stackoverflow.com/questions/4730152/what-indicates-an-office-open-xml-cell-contains-a-date-time-value
//
// Format examples:
//
// * "[$-404]e/m/d"
// * "[$-414]mmmm\ yyyy;@"
// * "[$-ru-RU]dd.mm.yyyy;@"
// * "[$-x-sysdate]dddd, mmmm dd, yyyy"
//
var DATE_FORMAT_SPECIFIC_LOCALE_PREFIX = /^\[\$-[^\]]+\]/;

// On some date formats, there's a ";@" suffix.
// It instructs the spreadsheet editor application to display any non-numeric
// value as is instead of hiding it or something like that.
//
// For example, if one inputs "Some text" instead of a date in such cell,
// it will still show "Some text" instead of an empty cell, even though
// the value is strictly-speaking invalid.
//
// Specifically, ";" means "anything before this applies only to a numeric value,
// while anything after it applies to a text value". And a follow-up "@" means
// "for a text value, just output it as is".
//
// It's not really clear why would anyone add such a feature to a format.
// Perhaps it feels more "user-friendly" towards a non-"tech-savvy" user
// of a spreadsheet editor application.
//
// Format examples:
//
// * "m/d/yyyy;@"
// * "[$-414]mmmm\ yyyy;@"
//
var DATE_FORMAT_ALLOW_ANY_OTHER_TEXT_SUFFIX = /;@$/;
var CACHE = {};
function isDateFormatCached(template) {
  if (template in CACHE) {
    return CACHE[template];
  }
  var result = isDateFormat(template);
  CACHE[template] = result;
  return result;
}
function isDateFormat(template) {
  // Date format tokens could be in upper case or in lower case.
  // There seems to be no single standard.
  // So the template is lowercased first.
  template = template.toLowerCase();

  // On some date formats, there's an "[$-...]" prefix.
  // It forces a specific locale to be used when formatting a date.
  template = template.replace(DATE_FORMAT_SPECIFIC_LOCALE_PREFIX, '');

  // On some date formats, there's an ";@" suffix.
  // It's not clear why would anyone need it in a date format template.
  // Still, because it occurs there, it should be stripped.
  template = template.replace(DATE_FORMAT_ALLOW_ANY_OTHER_TEXT_SUFFIX, '');

  // Extract all alphabetic parts from what's left from the template string.
  // Example: "mm/dd/yyyy" → ["mm", "dd", "yyyy"]
  var tokens = template.split(/\W+/);

  // If no alphabetic parts are present in what's left from the template string
  // then it could be any kind of template such as a generic numeric template
  // such as "$#,##0.00" currency template or "0.0%" percentage template.
  if (tokens.length < 0) {
    return false;
  }
  for (var _iterator = _createForOfIteratorHelperLoose(tokens), _step; !(_step = _iterator()).done;) {
    var token = _step.value;
    // If a non-date-format-specific alphabetic substring is found,
    // this might not necessarily be a date format.
    if (DATE_TEMPLATE_TOKENS.indexOf(token) < 0) {
      return false;
    }
  }
  return true;
}

// These tokens could be in upper case or in lower case.
// There seems to be no single standard, so using lower case.
var DATE_TEMPLATE_TOKENS = [
// Seconds (min two digits). Example: "05".
'ss',
// Minutes (min two digits). Example: "05". Could also be "Months". Weird.
'mm',
// Hours. Example: "1".
'h',
// Hours (min two digits). Example: "01".
'hh',
// "AM" part of "AM/PM". Lowercased just in case.
'am',
// "PM" part of "AM/PM". Lowercased just in case.
'pm',
// Day. Example: "1"
'd',
// Day (min two digits). Example: "01"
'dd',
// Month (numeric). Example: "1".
'm',
// Month (numeric, min two digits). Example: "01". Could also be "Minutes". Weird.
'mm',
// Month (shortened month name). Example: "Jan".
'mmm',
// Month (full month name). Example: "January".
'mmmm',
// Two-digit year. Example: "20".
'yy',
// Full year. Example: "2020".
'yyyy',
// I don't have any idea what "e" means.
// It's used in "built-in" XLSX formats:
// * 27 '[$-404]e/m/d';
// * 36 '[$-404]e/m/d';
// * 50 '[$-404]e/m/d';
// * 57 '[$-404]e/m/d';
'e'];
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