function GetFileName (filePath)
{
	let fileName = filePath;

	let firstParamIndex = fileName.indexOf ('?');
	if (firstParamIndex !== -1) {
		fileName = fileName.substring (0, firstParamIndex);
	}

	let firstSeparator = fileName.lastIndexOf ('/');
	if (firstSeparator === -1) {
		firstSeparator = fileName.lastIndexOf ('\\');
	}
	if (firstSeparator !== -1) {
		fileName = fileName.substring (firstSeparator + 1);
	}

	return decodeURI (fileName);
}
Used internally if a file is originated by a compressed archive.