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

Download my free JavaScript Beginner's Handbook!


Check out my in-depth, practical Web Development Courses!

(all 50% off with the coupon code POSITIVEVIBRATIONS)

⤴️⤴️⤴️

And signup to my upcoming JavaScript Bootcamp!

⤴️⤴️⤴️