How do JavaScript Proxy and Reflect work, and what are practical use cases?

Proxy intercepts object operations

const reactive = new Proxy({ count: 0 }, {
  get(target, key) { console.log(`Read: ${key}`); return Reflect.get(target, key); },
  set(target, key, value) { console.log(`Write: ${key} = ${value}`); Reflect.set(target, key, value); scheduleRerender(); return true; }
});
reactive.count;      // "Read: count"
reactive.count = 5;  // "Write: count = 5", triggers rerender

Use Case	How Proxy Helps
Validation	Intercept set, validate before writing
Reactivity	Track reads/writes for re-rendering
Default values	Return defaults for missing properties
API client	api.users.getById(1) → /users/1

Reflect provides default behavior for proxy traps — always delegate to it.