WP Locale to PHP & jQuery date format

/**
* Get the correct localized date formatting by WordPress Locale.
*
* Retrieves the short or full date formatting for PHP and jQuery (Date Picker) by WordPress Locale.
* (WordPress Dashboard -> Settings -> General)
*
* Formats are based on the official ICU formatting. This resource bypasses the need for the Intl module.
* The JSON file 'wp-locale-to-date-format.json' is located here: https://pastebin.com/eT3ku5fR
*/
function stonehenge_localize_date_format( $type = 'php', $length = 'short' ) {
    $json       = file_get_contents( __DIR__ . '/wp-locale-to-date-format.json' );
    $locales    = json_decode( $json, true );
    $locale     = str_replace( '_formal', '', determine_locale() );     // Dates are not different in formal.
    return array_key_exists( $locale, $locales ) ? $locales[$locale][$type][$length] : ($type != 'jquery' ? 'Y-m-d' : 'yy-mm-dd');
}

/**
* Localize the date for PHP output.
* Usage:
* echo stonehenge_localize_date( $value );              => 26-01-2021 (d-m-Y)
* echo stonehenge_localize_date( $value, 'full' );      => dinsdag 26 januari 2021 (l j F Y)
*/
function stonehenge_localize_date( $date, $length = 'short' ) {
    $date   = is_numeric( $date ) ? $date : strtotime( $date );     // Prevent errors.
    $format = stonehenge_localize_date_format( 'php', $length );
    return date_i18n( $format, $input );
}

/**
* Localize jQuery Date Picker by WordPress Locale.
*/
function stonehenge_localize_datepicker( $type ) {
    global $wp_locale;
    switch( $type ) {
        case 'months_full':
            $values = array_values( $wp_locale->month );
        break;
        case 'months_short':
            $values = array_values( $wp_locale->month_abbrev );
        break;
        case 'weekdays_full':
            $values = array_values( $wp_locale->weekday );
        break;
        case 'weekdays_short':
            $values = array_values( $wp_locale->weekday_abbrev );
        break;
    }
    return array_map( 'ucfirst', $values );     // Correction, as most languages only use lowercase mid-sentence.
}

/**
* Use wp_localize_script() to send the localized jQuery date picker options.
*/
wp_localize_script( 'your-script-handle', 'your-object-name', array(
    'dateFormat' => stonehenge_localize_date_format( 'jquery', 'short' ),
    'monthNames' => stonehenge_localize_datepicker( 'months_full' ),
    'monthNamesShort' => stonehenge_localize_datepicker( 'months_short' ),
    'dayNames' => stonehenge_localize_datepicker( 'weekdays_full' ),
    'dayNamesShort' => stonehenge_localize_datepicker( 'weekdays_short' ),
    'firstDay' => get_option( 'start_of_week' ),
    'prevText' => __('Previous'),
    'nextText' => __('Next'),
    'currentText' => __('Today')
) );

/**
* Call the localized values in your script.js
*/
jQuery(document).ready( function($) {
    $.datepicker({
        dateFormat: object.dateFormat,              // dd-mm-yy
        monthNames: object.monthNames,              // Januari, Februari, Maart, April ...
        monthNamesShort: object.monthNamesShort,    // Jan, Feb, Maa, Apr ...
        dayNames: object.dayNames,                  // Zondag, Maandag, Dinsdag, Woensdag ...
        dayNamesShort: object.dayNamesShort,        // Zo, Ma, Di, Wo ...
        firstDay: object.firstDay,                  // 1 (Monday)
        prevText: object.prevText,                  // Vorige
        nextText: object.nextText,                  // Volgende
        currentText: object.currentText,            // Vandaag
        yearRange: "-1:+4",                         // 2020 - 2025
        changeMonth: true,
        changeYear: true
    });
});