Explain why that code is marked as WRONG?

Technology CommunityCategory: TypeScriptExplain why that code is marked as WRONG?
VietMX Staff asked 1 year ago
/* WRONG */
interface Fetcher {
    getObject(done: (data: any, elapsedTime?: number) => void): void;

Don’t use optional parameters in callbacks unless you really mean it. This code has a very specific meaning: the done callback might be invoked with 1 argument or might be invoked with 2 arguments. The author probably intended to say that the callback might not care about the elapsedTime parameter, but there’s no need to make the parameter optional to accomplish this – it’s always legal to provide a callback that accepts fewer arguments.