script.js

document.addEventListener("DOMContentLoaded", function () {
    const language_links = document.querySelectorAll('.wpml-ls-link');

    for (const language_link of language_links) {
        language_link.addEventListener('click', function handleClick(event) {
            event.preventDefault();

            let languages = this.getElementsByClassName('wpml-ls-native');

            for (const language of languages) {
                let language_tag = language.getAttribute('lang');
                let language_href = language.parentElement.getAttribute('href');

                // Delete old WPML cookie.
                document.cookie = 'wp-wpml_current_language=; expires=Thu, 01 Jan 1970 00:00:00 UTC; path=/';
                document.cookie = '_icl_visitor_lang_js=; expires=Thu, 01 Jan 1970 00:00:00 UTC; path=/';

                // Set new cookie for selected language.
                document.cookie = 'wp-wpml_current_language=' + language_tag;
                document.cookie = '_icl_visitor_lang_js=' + language_tag;

                window.location.href = language_href;
            }
        });
    }
});