Enqueuing WordPress scripts - all pages, just posts, just certain templates

gistfile1.txt

function 8ii010b_scripts() {
 
    // this adds your script to all pages on the site
    wp_enqueue_script( 'custom-8ii010-js', get_template_directory_uri() . '/js/YOUR-JS-FILE.js', array(), '20151215', true );
 
    // this adds your script to all single posts
    if ( is_singular('post') ) {
        wp_enqueue_script( 'custom-8ii010-js', get_template_directory_uri() . '/js/YOUR-JS-FILE.js', array(), '20151215', true );
    }
 
    // this adds your script only to a certain  custom page template
    if ( is_page_template('page-about.php') ) {
        wp_enqueue_script( 'custom-8ii010-js', get_template_directory_uri() . '/js/YOUR-JS-FILE.js', array(), '20151215', true );
    }
}
add_action( 'wp_enqueue_scripts', '8ii010b_scripts' );