Source code for https://formidable-masterminds.com/firefox-default-value-bug-the-work-around/

firefox-default-value-bug-the-work-around.js

<script>
jQuery(document).ready(function($) {
    "use strict";

    /* self-executing function */
    ( function($) {

        /* this function is a workaround for an apparent Firefox bug
         * where the default values are sometimes not being displayed
         * the test form works Safari, Chrome, and Firefox Developer Edition.
         */
        function masterminds_maybe_set_default_radio_values() {
            /* this code works with radio buttons. It can be modified to work
             * with other field types
             */
            if ( ! $('input[id^="field_w3cfrm_post_content_type-"], input[id^="field_w3cfrm_post_content_format-"]').is(':checked') ) {
                $('input[id="field_w3cfrm_post_content_type-0"]').prop("checked", true);
                $('input[id="field_w3cfrm_post_content_format-0"]').prop("checked", true);
            }
        }
    
        masterminds_maybe_set_default_radio_values();

    })(jQuery);
});
</script>