Skip to content

The Object isPrototypeOf() method

Find out all about the JavaScript isPrototypeOf() method of an object

Called on an object instance, accepts an object as argument. If the object you called isPrototypeOf() on appears in the prototype chain of the object passed as argument, it returns true. Otherwise it returns false.

Example:

const Animal = {
  isAnimal: true
}

const Mammal = Object.create(Animal)
Mammal.isMammal = true

Animal.isPrototypeOf(Mammal) //true

const dog = Object.create(Animal)
Object.setPrototypeOf(dog, Mammal)

Animal.isPrototypeOf(dog) //true
Mammal.isPrototypeOf(dog) //true

→ Here's my latest YouTube video

→ Get my JavaScript Beginner's Handbook

→ I wrote 17 books to help you become a better developer, download them all at $0 cost by joining my newsletter

JOIN MY CODING BOOTCAMP, an amazing cohort course that will be a huge step up in your coding career - covering React, Next.js - next edition February 2025

Bootcamp 2025

Join the waiting list