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FLAVIO COPES
flaviocopes.com
2026

The Object setPrototypeOf() method

By Flavio Copes

Learn how the JavaScript Object.setPrototypeOf() method sets the prototype of an object, accepting the object and the prototype you want to assign.

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Set the prototype of an object.

While you’re here, see my guide on JavaScript Prototypal Inheritance

Accepts two arguments: the object and the prototype.

Usage:

Object.setPrototypeOf(object, prototype)

Example:

const Animal = {}
Animal.isAnimal = true

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

console.log('-------')
Mammal.isAnimal //true

const dog = Object.create(Animal)

dog.isAnimal  //true
console.log(dog.isMammal)  //undefined

Object.setPrototypeOf(dog, Mammal)

console.log(dog.isAnimal) //true
console.log(dog.isMammal) //true
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