A snippet of code to be added to the \Magento\Framework\View\Asset\Bundle\Manager::isValidAsset function, to create a list of JS files associated with an M2 storefront

isValidAsset Snippet

$destinationFile = "assets/js.txt";
$name = $asset->getPath();
$nameParts = explode('.', $name);
$extension = array_pop($nameParts);
if ($extension == 'js') {
    file_put_contents($destinationFile, $name.PHP_EOL , FILE_APPEND | LOCK_EX);
}