68 lines
2.4 KiB
Markdown
68 lines
2.4 KiB
Markdown
|
---
|
|||
|
id: 587d7db1367417b2b2512b86
|
|||
|
title: Reset an Inherited Constructor Property
|
|||
|
challengeType: 1
|
|||
|
videoUrl: ''
|
|||
|
localeTitle: 重置继承的构造函数属性
|
|||
|
---
|
|||
|
|
|||
|
## Description
|
|||
|
<section id="description">当一个对象从另一个对象继承它的<code>prototype</code> ,它也继承了<code>supertype</code>的构造函数属性。这是一个例子: <blockquote>函数Bird(){} <br> Bird.prototype = Object.create(Animal.prototype); <br> let duck = new Bird(); <br> duck.constructor // function Animal(){...} </blockquote>但<code>duck</code>和所有<code>Bird</code>实例都应该表明它们是由<code>Bird</code>而不是<code>Animal</code>建造的。为此,您可以手动将<code>Bird's</code>构造函数属性设置为<code>Bird</code>对象: <blockquote> Bird.prototype.constructor = Bird; <br> duck.constructor // function Bird(){...} </blockquote></section>
|
|||
|
|
|||
|
## Instructions
|
|||
|
<section id="instructions">修复代码,使<code>duck.constructor</code>和<code>beagle.constructor</code>返回各自的构造函数。 </section>
|
|||
|
|
|||
|
## Tests
|
|||
|
<section id='tests'>
|
|||
|
|
|||
|
```yml
|
|||
|
tests:
|
|||
|
- text: <code>Bird.prototype</code>应该是<code>Animal</code>一个实例。
|
|||
|
testString: 'assert(Animal.prototype.isPrototypeOf(Bird.prototype), "<code>Bird.prototype</code> should be an instance of <code>Animal</code>.");'
|
|||
|
- text: <code>duck.constructor</code>应该返回<code>Bird</code> 。
|
|||
|
testString: 'assert(duck.constructor === Bird, "<code>duck.constructor</code> should return <code>Bird</code>.");'
|
|||
|
- text: <code>Dog.prototype</code>应该是<code>Animal</code>一个实例。
|
|||
|
testString: 'assert(Animal.prototype.isPrototypeOf(Dog.prototype), "<code>Dog.prototype</code> should be an instance of <code>Animal</code>.");'
|
|||
|
- text: <code>beagle.constructor</code>应该返回<code>Dog</code> 。
|
|||
|
testString: 'assert(beagle.constructor === Dog, "<code>beagle.constructor</code> should return <code>Dog</code>.");'
|
|||
|
|
|||
|
```
|
|||
|
|
|||
|
</section>
|
|||
|
|
|||
|
## Challenge Seed
|
|||
|
<section id='challengeSeed'>
|
|||
|
|
|||
|
<div id='js-seed'>
|
|||
|
|
|||
|
```js
|
|||
|
function Animal() { }
|
|||
|
function Bird() { }
|
|||
|
function Dog() { }
|
|||
|
|
|||
|
Bird.prototype = Object.create(Animal.prototype);
|
|||
|
Dog.prototype = Object.create(Animal.prototype);
|
|||
|
|
|||
|
// Add your code below this line
|
|||
|
|
|||
|
|
|||
|
|
|||
|
let duck = new Bird();
|
|||
|
let beagle = new Dog();
|
|||
|
|
|||
|
```
|
|||
|
|
|||
|
</div>
|
|||
|
|
|||
|
|
|||
|
|
|||
|
</section>
|
|||
|
|
|||
|
## Solution
|
|||
|
<section id='solution'>
|
|||
|
|
|||
|
```js
|
|||
|
// solution required
|
|||
|
```
|
|||
|
</section>
|