function findConfigFile(searchPath) {
        var fileName = "tsconfig.json";
        while (true) {
            if (ts.sys.fileExists(fileName)) {
                return fileName;
            }
            var parentPath = ts.getDirectoryPath(searchPath);
            if (parentPath === searchPath) {
                break;
            }
            searchPath = parentPath;
            fileName = "../" + fileName;
        }
        return undefined;
    }
The version of the TypeScript compiler release