Object.create usage in Javascript - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this code using Object.create?

Consider the following JavaScript code. What will be logged to the console?

Javascript

const parent = { greeting: 'Hello' };
const child = Object.create(parent);
child.greeting = 'Hi';
console.log(child.greeting);

A "Hi"

B "Hello"

C undefined

D TypeError

💡 Hint

Remember that properties set directly on the child object override those from the prototype.

The child object has its own 'greeting' property set to 'Hi', so it logs 'Hi'. The parent's 'greeting' is shadowed.

❓ Predict Output

intermediate

What does this code output when accessing inherited property?

Look at this code snippet. What will be the output of the console.log statement?

Javascript

const animal = { eats: true };
const rabbit = Object.create(animal);
console.log(rabbit.eats);

A true

B false

C undefined

D ReferenceError

💡 Hint

Object.create sets the prototype, so properties can be inherited.

The 'rabbit' object inherits 'eats' from 'animal', so it logs true.

❓ Predict Output

advanced

What is the output of this code with property descriptors?

Analyze this code. What will be printed to the console?

Javascript

const proto = { x: 10 };
const obj = Object.create(proto, {
  y: { value: 20, writable: false, enumerable: true, configurable: true }
});
obj.y = 30;
console.log(obj.y);

A undefined

B 30

C 20

D TypeError

💡 Hint

Writable: false means the property cannot be changed.

The property 'y' is not writable, so the assignment to 30 fails silently and 'y' remains 20.

❓ Predict Output

advanced

What error does this code raise?

What error will this code produce when run?

Javascript

const obj = Object.create(null);
console.log(obj.toString());

A ReferenceError: toString is not defined

B undefined

C [object Object]

D TypeError: obj.toString is not a function

💡 Hint

Object.create(null) creates an object with no prototype.

Since obj has no prototype, it does not have the toString method, causing a TypeError.

🧠 Conceptual

expert

Which option correctly creates an object with a prototype and a new method?

You want to create an object 'car' that inherits from 'vehicle' and adds a method 'drive'. Which code does this correctly?

A

const vehicle = { wheels: 4 };
const car = Object.create(vehicle);
car.drive = function() { return 'Driving'; };

B

const vehicle = { wheels: 4 };
const car = Object.create(vehicle, { drive: { value: function() { return 'Driving'; }, enumerable: true } });

C

const vehicle = { wheels: 4 };
const car = Object.create(vehicle, { drive: { value: () => 'Driving' } });

D

const vehicle = { wheels: 4 };
const car = Object.create(vehicle, { drive: () => 'Driving' });

💡 Hint

Remember that the second argument of Object.create expects property descriptors.

Option B correctly uses a property descriptor with a function value and sets enumerable true. Option B misses enumerable, A adds method after creation, D uses wrong descriptor syntax.