Prototype chain in Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the prototype chain in JavaScript?

The prototype chain is a series of linked objects used to look up properties and methods. When you try to access a property on an object, JavaScript checks the object first. If it doesn't find it, it looks up the prototype chain until it finds the property or reaches the end.

beginner

How does JavaScript find a property on an object using the prototype chain?

JavaScript first checks the object itself. If the property is not there, it checks the object's prototype. This continues up the chain until the property is found or the chain ends at null.

intermediate

What is the role of Object.prototype in the prototype chain?

Object.prototype is the last object in the prototype chain. It provides common methods like toString() and hasOwnProperty(). Its prototype is null, which ends the chain.

intermediate

Explain how the prototype chain enables inheritance in JavaScript.

Inheritance happens because objects can access properties and methods from their prototype. If a property is not found on the object, JavaScript looks up the prototype chain, allowing objects to share behavior without copying code.

beginner

What happens if a property is not found anywhere in the prototype chain?

If the property is not found on the object or any object in its prototype chain, JavaScript returns undefined.

What does JavaScript check first when accessing a property on an object?

A The object itself

B The object's prototype

C Object.prototype

D The global object

JavaScript first checks the object itself before looking up the prototype chain.

What is the prototype of Object.prototype?

A null

B Object.prototype

C undefined

D The global object

Object.prototype's prototype is null, which ends the prototype chain.

If a property is not found on an object or its prototype chain, what is returned?

A null

B undefined

C false

D An error is thrown

JavaScript returns undefined when a property is not found anywhere in the prototype chain.

Which of these is true about the prototype chain?

A It is a feature of the JavaScript compiler

B It copies all properties from the prototype to the object

C It only works with arrays

D It allows objects to inherit properties and methods

The prototype chain allows objects to inherit properties and methods by linking to their prototypes.

How can you access an object's prototype in JavaScript?

A Using object.constructor

B Using object.prototype

C Using __proto__ or Object.getPrototypeOf()

D Using object.prototypeChain

You can access an object's prototype using __proto__ or the Object.getPrototypeOf() method.

Describe the prototype chain and how JavaScript uses it to find properties.

Think about how JavaScript checks the object and then moves up to prototypes.

Explain how inheritance works in JavaScript using the prototype chain.

Focus on how objects get behavior from their prototypes.