JS Practice — Built-in Objects

hasOwnProperty() — vs inherited

📖 Usage Example

// Check for own (non-inherited) property
const obj = { a: 1 }
obj.hasOwnProperty('a')          // → true
obj.hasOwnProperty('toString')   // → false

Use hasOwnProperty() to check whether a property exists directly on an object rather than on its prototype chain.

hasOwnProperty() — own vs inherited

The key difference between hasOwnProperty() and the in operator is that in checks the entire prototype chain, while hasOwnProperty() only checks the object itself.

Challenge: Show the difference between in and hasOwnProperty().

💡 Hints (1)

• hasOwnProperty checks only own props; in checks the full prototype chain