Answers for "add css and js in wordpress"

adding css and js files using action hook

function add_theme_scripts() {
  wp_enqueue_style( 'style', get_stylesheet_uri() );
 
  wp_enqueue_style( 'slider', get_template_directory_uri() . '/css/slider.css', array(), '1.1', 'all');
 
  wp_enqueue_script( 'script', get_template_directory_uri() . '/js/script.js', array ( 'jquery' ), 1.1, true);
 
    if ( is_singular() && comments_open() && get_option( 'thread_comments' ) ) {
      wp_enqueue_script( 'comment-reply' );
    }
}
add_action( 'wp_enqueue_scripts', 'add_theme_scripts' );

how to add css file in wordpress

wp_enqueue_style( 'style', get_stylesheet_uri() );

wordpress include javascript file

function jquery_tabify() {
    wp_enqueue_script(
        'jquery-tabify',
        'http://site.com/jquery.tabify.js',
        array( 'jquery' )
    );
}
add_action( 'wp_enqueue_scripts', 'jquery_tabify' );