freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/object-oriented-programming/verify-an-objects-constructor-with-instanceof.english.md

id, title, challengeType

id	title	challengeType
587d7dae367417b2b2512b7a	Verify an Object's Constructor with instanceof	1

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; // => 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; // => 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.

Tests

tests:
  - text: <code>myHouse</code> should have a <code>numBedrooms</code> attribute set to a number.
    testString: 'assert(typeof myHouse.numBedrooms === "number", "<code>myHouse</code> should have a <code>numBedrooms</code> attribute set to a number.");'
  - text: Be sure to verify that <code>myHouse</code> is an instance of <code>House</code> using the <code>instanceof</code> operator.
    testString: 'assert(/myHouse\s*instanceof\s*House/.test(code), "Be sure to verify that <code>myHouse</code> is an instance of <code>House</code> using the <code>instanceof</code> operator.");'

Challenge Seed

/* jshint expr: true */

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

// Add your code below this line

Solution

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