How to add “active” class to wp_nav_menu() current menu item (simple way)

Question

I am creating custom Wordpress theme using a starter theme _Underscores. I am also using Bootstrap as a front-end framework.

I would like to modify wp_nav_menu so th

Answer 1

In header.php insert this code to show menu:

 'menu-one',
            'walker' => new Custom_Walker_Nav_Menu_Top
        )
    );
?>

In functions.php use this:

class Custom_Walker_Nav_Menu_top extends Walker_Nav_Menu
{
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
        $is_current_item = '';
        if(array_search('current-menu-item', $item->classes) != 0)
        {
            $is_current_item = ' class="active"';
        }
        echo ''.$item->title;
    }

    function end_el( &$output, $item, $depth = 0, $args = array() ) {
        echo '