PreParsePostFormat

Pre-parse / Post-format lets you process the input before the parser and process the string output after the formatter. Based on similar behavior for locales in moment.js.

NOTE: this plugin requires the localeData plugin to be imported before it (as it depends on it's functionality).

NOTE: this plugin also affects the relative time plugin, also by design (mimics the moment.js implementaiton behavior).

Sample usage

e.g. In the AR locale specifically, it is used to support Arabic numerals.

// Arabic [ar]
import dayjs from 'dayjs';
import preParsePostFormat from 'dayjs/plugin/preParsePostFormat';
dayjs.extend(preParsePostFormat);

const months =
  'يناير_فبراير_مارس_أبريل_مايو_يونيو_يوليو_أغسطس_سبتمبر_أكتوبر_نوفمبر_ديسمبر'.split(
    '_'
  );
const symbolMap = {
  1: '١',
  2: '٢',
  3: '٣',
  4: '٤',
  5: '٥',
  6: '٦',
  7: '٧',
  8: '٨',
  9: '٩',
  0: '٠',
};

const numberMap = {
  '١': '1',
  '٢': '2',
  '٣': '3',
  '٤': '4',
  '٥': '5',
  '٦': '6',
  '٧': '7',
  '٨': '8',
  '٩': '9',
  '٠': '0',
};

const locale = {
  name: 'ar',
  // ...
  preparse(string) {
    return string
      .replace(/[١٢٣٤٥٦٧٨٩٠]/g, match => numberMap[match])
      .replace(/،/g, ',');
  },
  postformat(string) {
    return string.replace(/\d/g, match => symbolMap[match]).replace(/,/g, '،');
  },
  // ...
};
// ...

The tests should also give you a good idea on how to use the plugin if this isn't clear enough 😉.