JS Practice — Built-in Objects

Object.hasOwn() — inherited property returns false

📖 Usage Example

// Check if a property is directly on the object
const obj = { name: 'Alice' }
Object.hasOwn(obj, 'name')      // → true
Object.hasOwn(obj, 'toString')  // → false

Use Object.hasOwn() to reliably check if a property is an own property, without being fooled by inherited properties.

Object.hasOwn() — own vs inherited

The in operator finds inherited properties, but Object.hasOwn does not — it is strictly limited to own properties.

Challenge: Implement ownVsInherited(proto, obj, key) that returns an object with ownResult (from Object.hasOwn) and inResult (from key in obj).

const proto = { x: 1 }
const obj = Object.create(proto)
ownVsInherited(proto, obj, 'x')
// → { ownResult: false, inResult: true }

💡 Hints (1)

• `in` traverses the prototype chain; `Object.hasOwn` does not.