BeforeBackendPageRenderEvent 

The PSR-14 event \TYPO3\CMS\Backend\Controller\Event\BeforeBackendPageRenderEvent is dispatched in the \TYPO3\CMS\Backend\Controller\BackendController before the main backend page is rendered.

The event allows extensions to inject custom assets into the backend top frame by providing access to the following properties:

• $view ( \TYPO3\CMS\Core\View\ViewInterface ) – assign additional template variables to the backend top frame view
• $javaScriptRenderer ( \TYPO3\CMS\Core\Page\JavaScriptRenderer ) – add custom JavaScript modules to the backend top frame
• $pageRenderer ( \TYPO3\CMS\Core\Page\PageRenderer ) – add further assets such as CSS files (marked @internal)

<?php

declare(strict_types=1);

namespace MyVendor\MyExtension\Backend\EventListener;

use TYPO3\CMS\Backend\Controller\Event\BeforeBackendPageRenderEvent;
use TYPO3\CMS\Core\Attribute\AsEventListener;
use TYPO3\CMS\Core\Page\JavaScriptModuleInstruction;

#[AsEventListener(
    identifier: 'my-extension/backend/before-backend-page-render',
)]
final readonly class MyEventListener
{
    public function __invoke(BeforeBackendPageRenderEvent $event): void
    {
        $event->javaScriptRenderer->addJavaScriptModuleInstruction(
            JavaScriptModuleInstruction::create(
                '@my-vendor/my-extension/backend-module.js',
            ),
        );
    }
}