这边是把es6的类用作类型去判定的意思不，有点不理解

[coderDGJ]

class ApiError extends Error {
code: number = 0;
}
class HttpError extends Error {
statusCode: number = 200;
}

function isApiError(error: Error) {
if (typeof (error as ApiError).code === 'number') {
return true;
}
return false;
}