freeCodeCamp/curriculum/challenges/chinese/02-javascript-algorithms-and-data-structures/object-oriented-programming/use-a-constructor-to-create-objects.md

---
id: 587d7dad367417b2b2512b78
title: Use a Constructor to Create Objects
challengeType: 1
forumTopicId: 18233
dashedName: use-a-constructor-to-create-objects
---

# --description--

Here's the `Bird` constructor from the previous challenge:

```js
function Bird() {
  this.name = "Albert";
  this.color  = "blue";
  this.numLegs = 2;
  // "this" inside the constructor always refers to the object being created
}

let blueBird = new Bird();
```

Notice that the `new` operator is used when calling a constructor. This tells JavaScript to create a new instance of `Bird` called `blueBird`. Without the `new` operator, `this` inside the constructor would not point to the newly created object, giving unexpected results. Now `blueBird` has all the properties defined inside the `Bird` constructor:

```js
blueBird.name; // => Albert
blueBird.color; // => blue
blueBird.numLegs; // => 2
```

Just like any other object, its properties can be accessed and modified:

```js
blueBird.name = 'Elvira';
blueBird.name; // => Elvira
```

# --instructions--

Use the `Dog` constructor from the last lesson to create a new instance of `Dog`, assigning it to a variable `hound`.

# --hints--

`hound` should be created using the `Dog` constructor.

```js
assert(hound instanceof Dog);
```

Your code should use the `new` operator to create an instance of `Dog`.

```js
assert(code.match(/new/g));
```

# --seed--

## --seed-contents--

```js
function Dog() {
  this.name = "Rupert";
  this.color = "brown";
  this.numLegs = 4;
}
// Only change code below this line
```

# --solutions--

```js
function Dog() {
  this.name = "Rupert";
  this.color = "brown";
  this.numLegs = 4;
}
const hound = new Dog();
```