This is my Javascript code:

document.addEventListener("DOMContentLoaded", function() {
    console.log("DOM fully loaded and parsed");

    const tableRows = document.querySelectorAll('.table--symlist2 tbody tr');
    console.log("Table rows:", tableRows);

    let currentCountryClass = "";
    let isOdd = true;

    tableRows.forEach((row) => {
        // Get the country class (assumes it's the first class in the classList)
        let rowCountryClass = Array.from(row.classList).find(cls => cls.startsWith('w-'));
        console.log("Current row country class:", rowCountryClass);

        if (rowCountryClass !== currentCountryClass) {
            // New country group
            currentCountryClass = rowCountryClass;
            isOdd = !isOdd; // Flip the isOdd flag for the new group
        }

        // Apply the appropriate class
        if (isOdd) {
            row.classList.add('odd');
            console.log("Added 'odd' class to row:", row);
        } else {
            row.classList.add('even');
            console.log("Added 'even' class to row:", row);
        }
    });
});

And this is the code I inserted in my functions.php file to include it:

function my_custom_scripts() {
    wp_enqueue_script('custom-js', get_stylesheet_directory_uri() . '/custom.js', array('jquery'), null, true);
}
add_action('wp_enqueue_scripts', 'my_custom_scripts');

It looks like Javascript is enabled by default on Opera. In addition, I added this specific site for good measure, but it still doesn't work.