Explain how the `instanceof` operator works.

Q: Explain how the `instanceof` operator works.

It checks if a specific **constructor's prototype** exists anywhere in that object's **prototype chain.** class Animal {} class Dog extends Animal {} const myPet = new Dog(); console.log(myPet instanceof Dog); // true console.log(myPet instanceof Animal); // true (because of inheritance) console.log(myPet instanceof Object); // true (everything leads back to Object) Even though strings have Object Wrappers, literal primitives are not considered instances of their constructors

Difficulty: 4/10

prototype chain, type checking, cross-realm behavior

The `instanceof` operator checks whether an object is an instance of a particular constructor function or class. It traverses the prototype chain of the object, looking for a match with the prototype of the constructor function.

It checks if a specific constructor's prototype exists anywhere in that object's prototype chain.

javascript

1
Even though strings have Object Wrappers, literal primitives are not considered instances of their constructors

Scenario Questions

0-2 years experience

Follow-up Questions

Explain how the `instanceof` operator works.

Difficulty: 4/10

prototype chain, type checking, cross-realm behavior

The `instanceof` operator checks whether an object is an instance of a particular constructor function or class. It traverses the prototype chain of the object, looking for a match with the prototype of the constructor function.

It checks if a specific constructor's prototype exists anywhere in that object's prototype chain.

javascript

1
Even though strings have Object Wrappers, literal primitives are not considered instances of their constructors

Scenario Questions

0-2 years experience

Explain how the `instanceof` operator works.

The instanceof operator checks whether an object is an instance of a particular constructor function or class. It traverses the prototype chain of the object, looking for a match with the prototype of the constructor function.

Scenario Questions

Follow-up Questions

Explain how the `instanceof` operator works.

The instanceof operator checks whether an object is an instance of a particular constructor function or class. It traverses the prototype chain of the object, looking for a match with the prototype of the constructor function.

Scenario Questions

Follow-up Questions

The `instanceof` operator checks whether an object is an instance of a particular constructor function or class. It traverses the prototype chain of the object, looking for a match with the prototype of the constructor function.

The `instanceof` operator checks whether an object is an instance of a particular constructor function or class. It traverses the prototype chain of the object, looking for a match with the prototype of the constructor function.