JS Practice — Built-in Objects

Object.hasOwn() — works on null-prototype objects

📖 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() — null prototype objects

obj.hasOwnProperty throws on null-prototype objects because they don't inherit it. Object.hasOwn works safely on them.

Challenge: Implement checkNullProto(key, val) that creates a null-prototype object with the given key/val, then uses Object.hasOwn to check for that key.

checkNullProto('id', 42) // → true

💡 Hints (1)

• `Object.hasOwn` is a static method and never relies on the object's own `hasOwnProperty`.