Assets::getCheckSum

static function getCheckSum()
{
	static $result = null;

	if ($result !== null)
	{
		return $result;
	}

	$assetsData = [];

	$documentRoot = BitrixMainApplication::getDocumentRoot();
	foreach(self::$assetFiles as $filePath)
	{
		$file = new BitrixMainIOFile($documentRoot . $filePath);
		if (!$file->isExists())
		{
			continue;
		}

		$assetsData[] = [
			$filePath => $file->getModificationTime()
		];
	}

	return md5(serialize($assetsData));
}