Apa sing digunakake kanggo Proxy lan Reflect?

Question

IT Interview Practice · Accepted Answer

**Proxy** mbungkus sawijining objek lan ngidini kowe **intercept** operasi fundamental ing nggone (get, set, has, delete, dsb.) liwat fungsi handler sing diarani **traps**. **Reflect** nyediakake versi default saka operasi-operasi kasebut minangka fungsi, mula traps bisa nterusake marang perilaku normal kanthi bersih.

```js
const user = { name: "Ann" };

proxied.name;     // logs "read name" → "Ann"
proxied.age = -5; // throws — intercepted by the set trap
```

## Kasus nyata

- **Reactivity**: Sistem reactivity Vue 3 mbungkus state ing Proxy supaya ngerti tepat kapan kowe maca utawa nulis properti, lan re-render kanthi cocok.
- **Validation / access control**: nglakokne aturan ing property writes.
- **Logging / instrumentation**: trace access kanggo debugging.
- **Default values / virtual properties**: mbalekake nilai computed kanggo kunci sing ilang.
- **Negative array indices**, immutable wrappers, API clients sing generate methods kanthi dinamis.

## Mengapa Reflect ana

Sajroning trap kowe kudu nindakake operasi *default*. Nggunakake `Reflect.get/set` (tinimbang `target[key]`) nangani kanthi bener edge cases kaya `receiver` sing bener kanggo inherited getters/setters.

## Mengapa penting

Proxies ngaktifake meta-programming sing kuwat sing frameworks ngandelake.

Trade-off-e yaiku **overhead** — saben operasi pinarak liwat trap mu — mula gunakake ing panggonan interception pancen nesuake, ora kanggo objek saben dina.

Kasus nyata

Mengapa Reflect ana

Mengapa penting

Pitakon sing gegandhengan