Prototype chain in Javascript - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create an object that inherits from another object using __proto__.

Javascript

const parent = { greet() { return 'Hello'; } };
const child = { __proto__: [1] };
console.log(child.greet());

Drag options to blanks, or click blank then click option'

AObject

Bchild

Cparent

D{}

Attempts:

3 left

💡 Hint

Common Mistakes

Using the child object itself as prototype causes no inheritance.

Using Object or {} does not link to the parent object.

The __proto__ property sets the prototype of the object. Setting child.__proto__ = parent makes child inherit from parent.

2fill in blank

medium

Complete the code to check if 'greet' is in the prototype chain of child.

Javascript

const parent = { greet() { return 'Hi'; } };
const child = { __proto__: parent };
console.log([1] in child);

Drag options to blanks, or click blank then click option'

A'parent'

Bgreet

C'child'

D'greet'

Attempts:

3 left

💡 Hint

Common Mistakes

Using the property name without quotes causes a ReferenceError.

Checking for 'child' or 'parent' as strings is incorrect.

The in operator checks if a property exists in the object or its prototype chain. The property name must be a string.

3fill in blank

hard

Fix the error in the code to correctly set the prototype of child to parent using Object.setPrototypeOf.

Javascript

const parent = { say() { return 'Hey'; } };
const child = {};
Object.setPrototypeOf(child, [1]);
console.log(child.say());

Drag options to blanks, or click blank then click option'

Aparent

Bchild

C{}

DObject

Attempts:

3 left

💡 Hint

Common Mistakes

Passing child as the prototype causes no inheritance.

Passing {} or Object is incorrect.

Object.setPrototypeOf(obj, prototype) sets the prototype of obj. Here, child should inherit from parent.

4fill in blank

hard

Fill both blanks to create a prototype chain where grandChild inherits from child, and child inherits from parent.

Javascript

const parent = { speak() { return 'Hello'; } };
const child = { __proto__: [1] };
const grandChild = { __proto__: [2] };
console.log(grandChild.speak());

Drag options to blanks, or click blank then click option'

Aparent

Bchild

C{}

DgrandChild

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of prototypes.

Setting prototypes to empty objects breaks the chain.

Setting child.__proto__ = parent and grandChild.__proto__ = child creates a chain where grandChild inherits from child, which inherits from parent.

5fill in blank

hard

Fill all three blanks to create a prototype chain and check if 'speak' is accessible from grandChild.

Javascript

const parent = { speak() { return 'Hi'; } };
const child = { __proto__: [1] };
const grandChild = { __proto__: [2] };
console.log([3] in grandChild);

Drag options to blanks, or click blank then click option'

Aparent

Bchild

C'speak'

D'child'

Attempts:

3 left

💡 Hint

Common Mistakes

Using property names without quotes in 'in' operator.

Setting prototypes incorrectly breaks the chain.

The prototype chain is set by linking child to parent and grandChild to child. The in operator checks if 'speak' exists in grandChild or its prototypes.