JS Practice — Built-in Objects

Proxy deleteProperty trap — key removed from target

📖 Usage Example

const log = []
const p = new Proxy({}, {
  deleteProperty: (t, k) => { log.push(k); return true }
})
delete p.foo
console.log(log) // → ['foo']

The deleteProperty trap intercepts delete operations, allowing custom logic when a property is deleted from a proxy.

deleteProperty — passthrough removes key

After a passthrough delete, the property no longer exists on the proxy (or its target).

Challenge: Verify that after delete p.x, 'x' in p is false.

💡 Hints (1)

• A passthrough `delete` removes the key from the target, so `in` returns `false`.