Load js/css files only on specific admin UI pages

The right hooks

    // Use both for scripts & styles *)
    wp_enqueue_scripts // (for the frontend)
    login_enqueue_scripts // (for the login screen)
    admin_enqueue_scripts // (for the admin dashboard)

^{*) Read this article @wpdevel.}

Further reading in the Codex about the three hooks

• admin_menu
• network_admin_menu
• user_admin_menu

On the admin_enqueue_scripts hook, you have an argument as well: The $hook_suffix:

add_action( 'admin_enqueue_scripts', function( $hook )
{
    var_dump( $hook );
} );

Admin page hooks

When registering a admin (sub)menu page, you can save the result, which is the page hook, into a variable:

function register_admin_page()
{
    // Register (sub)menu page
    $hook_suffix = add_submenu_page( $your_args_array );
    // Add styles to hook
    add_action( "load-{$hook_suffix}", 'callback_function' );
}
// Use one of those hooks to register the page
add_action( 'admin_menu', 'register_admin_page' );
add_action( 'user_admin_menu', 'register_admin_page' );
add_action( 'network_admin_menu', 'register_admin_page' );

// Register your styles & scripts in here
function callback_function()
{
    // do stuff
}

Admin globally available variables to check against

The following

global $hook_suffix, $typenow, $pagenow, $self, $parent_file, $submenu_file

are available on a wide range of admin pages. Use them to check if you’re on the requested page that you need and only then do stuff.

// Example
if ( 'edit.php' !== $GLOBALS['pagenow'] )
    return;

Even better than testing against a variable, which can get reset on the fly (example) …

$GLOBALS['wp'] = array( 'lost', 'my', 'contents', );

… is using the \WP_Screen object on admin pages:

add_action( 'admin_enqueue_scripts', function( $hook )
{
    /** @var \WP_Screen $screen */
    $screen = get_current_screen();

    var_dump( $screen );
    if ( 'post.php' !== $screen->base )
        return;
} );