Using TYPO3 12.

I’m trying to add a JavaScript module to my backend module but I can’t get it working.

Here is what I’ve done by following the official documentation on this:

1. Register JS module in /Configuration/JavaScriptModules.php

return [
    'dependencies' => ['backend'],
    'imports' => [
        '@vendor/package/' => 'EXT:vendor/Resources/Public/JavaScript/',
    ],
];

2. Providing PageRenderer to the module controller via /Configuration/Services.yaml

VendeorpackageControllerBackendBackendModuleController:
    tags: ['backend.controller']
    arguments:
      $pageRenderer: '@TYPO3CMSCorePagePageRenderer'

3. Using loadJavaScriptModule to add the JS module to the page

    public function initializeAction(): void
    {
        $this->pageRenderer->loadJavaScriptModule('@vendor/package/backend-module.js');
    }

I already tried alternatives like accessing the JavaScriptRenderer directly via the PageRenderer or using the f:be.pageRenderer ViewHelper but nothing seems to work.

I could also verify by debugging that the JS file gets added to the JavaScriptRenderer and is inside its importMap. I’ve also checked all file paths for possible typos multiple times now.

What am I missing here?