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id	title	challengeType	forumTopicId	dashedName
587d7dae367417b2b2512b7a	Verify an Object's Constructor with instanceof	1	301337	verify-an-objects-constructor-with-instanceof

--description--

Anytime a constructor function creates a new object, that object is said to be an instance of its constructor. JavaScript gives a convenient way to verify this with the instanceof operator. instanceof allows you to compare an object to a constructor, returning true or false based on whether or not that object was created with the constructor. Here's an example:

let Bird = function(name, color) {
  this.name = name;
  this.color = color;
  this.numLegs = 2;
}

let crow = new Bird("Alexis", "black");

crow instanceof Bird;

This instanceof method would return true.

If an object is created without using a constructor, instanceof will verify that it is not an instance of that constructor:

let canary = {
  name: "Mildred",
  color: "Yellow",
  numLegs: 2
};

canary instanceof Bird;

This instanceof method would return false.

--instructions--

Create a new instance of the House constructor, calling it myHouse and passing a number of bedrooms. Then, use instanceof to verify that it is an instance of House.

--hints--

myHouse should have a numBedrooms attribute set to a number.

assert(typeof myHouse.numBedrooms === 'number');

You should verify that myHouse is an instance of House using the instanceof operator.

assert(/myHouse\s*instanceof\s*House/.test(code));

--seed--

--seed-contents--

function House(numBedrooms) {
  this.numBedrooms = numBedrooms;
}

// Only change code below this line

--solutions--

function House(numBedrooms) {
  this.numBedrooms = numBedrooms;
}
const myHouse = new House(4);
console.log(myHouse instanceof House);

1.8 KiB Raw Blame History