The Object isPrototypeOf() method
Find out all about the JavaScript isPrototypeOf() method of an object
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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 → Get my JavaScript Beginner's Handbook
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