JS Practice — Built-in Objects

Object.isExtensible() — after freeze

📖 Usage Example

// Check if new properties can be added
const obj = { a: 1 }
Object.isExtensible(obj)             // → true
Object.preventExtensions(obj)
Object.isExtensible(obj)             // → false

Use Object.isExtensible() to check whether new properties can still be added to an object.

Object.isExtensible() after freeze

Object.freeze(obj) makes an object non-extensible, non-configurable, and non-writable.

Challenge: Implement isFrozenAndNonExtensible(obj) that returns true when the object is both frozen and not extensible.

💡 Hints (1)

• freeze implies non-extensible