Can’t use admin_enqueue_scripts or wp_enqueue_script

Right now your error is that you forgot to enqueue them,

function theme_enqueue_scripts(){
    wp_register_script('modernizr', get_stylesheet_directory_uri()  . '/js/modernizr.js');
    wp_register_script('require', get_stylesheet_directory_uri()  . '/js/vendor/requirejs/require.js', array(), false, true);
    wp_register_script('global', get_stylesheet_directory_uri()  . '/js/global.js', array('require'), false, true);      
    wp_register_style('globalstyle', get_stylesheet_directory_uri()  . '/css/global.css');

    wp_enqueue_script( array('modernizr','require','global') );
    wp_enqueue_style ('globalstyle');
}
add_action('wp_enqueue_scripts', 'theme_enqueue_scripts');

function navigation_script() {
    wp_register_script('admin-nav', get_stylesheet_directory_uri()  . '/js/admin-nav.js',array(), null, true);

    wp_enqueue_script('admin-nav');
}
add_action( 'admin_enqueue_scripts', 'navigation_script' );