73 lines
2.3 KiB
Markdown
73 lines
2.3 KiB
Markdown
|
---
|
||
|
|
id: 587d7dad367417b2b2512b78
|
||
|
|
title: Use a Constructor to Create Objects
|
||
|
|
challengeType: 1
|
||
|
|
---
|
||
|
|
|
||
|
|
## Description
|
||
|
|
<section id='description'>
|
||
|
|
Here's the <code>Bird</code> constructor from the previous challenge:
|
||
|
|
<blockquote>function Bird() {<br> this.name = "Albert";<br> this.color = "blue";<br> this.numLegs = 2;<br> // "this" inside the constructor always refers to the object being created<br>}<br><br>let blueBird = new Bird();</blockquote>
|
||
|
|
Notice that the <code>new</code> operator is used when calling a constructor. This tells JavaScript to create a new <code>instance</code> of <code>Bird</code> called <code>blueBird</code>. Without the <code>new</code> operator, <code>this</code> inside the constructor would not point to the newly created object, giving unexpected results.
|
||
|
|
Now <code>blueBird</code> has all the properties defined inside the <code>Bird</code> constructor:
|
||
|
|
<blockquote>blueBird.name; // => Albert<br>blueBird.color; // => blue<br>blueBird.numLegs; // => 2</blockquote>
|
||
|
|
Just like any other object, its properties can be accessed and modified:
|
||
|
|
<blockquote>blueBird.name = 'Elvira';<br>blueBird.name; // => Elvira</blockquote>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
## Instructions
|
||
|
|
<section id='instructions'>
|
||
|
|
Use the <code>Dog</code> constructor from the last lesson to create a new instance of <code>Dog</code>, assigning it to a variable <code>hound</code>.
|
||
|
|
</section>
|
||
|
|
|
||
|
|
## Tests
|
||
|
|
<section id='tests'>
|
||
|
|
|
||
|
|
```yml
|
||
|
|
tests:
|
||
|
|
- text: <code>hound</code> should be created using the <code>Dog</code> constructor.
|
||
|
|
testString: 'assert(hound instanceof Dog, ''<code>hound</code> should be created using the <code>Dog</code> constructor.'');'
|
||
|
|
- text: Your code should use the <code>new</code> operator to create an <code>instance</code> of <code>Dog</code>.
|
||
|
|
testString: 'assert(code.match(/new/g), ''Your code should use the <code>new</code> operator to create an <code>instance</code> of <code>Dog</code>.'');'
|
||
|
|
|
||
|
|
```
|
||
|
|
|
||
|
|
</section>
|
||
|
|
|
||
|
|
## Challenge Seed
|
||
|
|
<section id='challengeSeed'>
|
||
|
|
|
||
|
|
<div id='js-seed'>
|
||
|
|
|
||
|
|
```js
|
||
|
|
function Dog() {
|
||
|
|
this.name = "Rupert";
|
||
|
|
this.color = "brown";
|
||
|
|
this.numLegs = 4;
|
||
|
|
}
|
||
|
|
// Add your code below this line
|
||
|
|
|
||
|
|
|
||
|
|
```
|
||
|
|
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</section>
|
||
|
|
|
||
|
|
## Solution
|
||
|
|
<section id='solution'>
|
||
|
|
|
||
|
|
|
||
|
|
```js
|
||
|
|
function Dog() {
|
||
|
|
this.name = "Rupert";
|
||
|
|
this.color = "brown";
|
||
|
|
this.numLegs = 4;
|
||
|
|
}
|
||
|
|
const hound = new Dog();
|
||
|
|
```
|
||
|
|
|
||
|
|
</section>
|