Body script

// Inserts a script before the closing WordPress body tag

function custom_enqueue_scripts(){

    wp_enqueue_script('script-name', 'https://code.jquery.com/jquery-3.3.1.slim.min.js', '', '', true);
    // Makes use of the $in_footer parameter which is set to true, this tells WordPress to put the script before closing body tag
}
add_action ('wp_enqueue_script', 'custom_enqueue_scripts');