68 lines
2.4 KiB
Markdown
68 lines
2.4 KiB
Markdown
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---
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id: 587d7db1367417b2b2512b86
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title: Reset an Inherited Constructor Property
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challengeType: 1
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videoUrl: ''
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localeTitle: 重置继承的构造函数属性
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---
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## Description
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<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>
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## Instructions
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<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>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>Bird.prototype</code>应该是<code>Animal</code>一个实例。
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testString: 'assert(Animal.prototype.isPrototypeOf(Bird.prototype), "<code>Bird.prototype</code> should be an instance of <code>Animal</code>.");'
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- text: <code>duck.constructor</code>应该返回<code>Bird</code> 。
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testString: 'assert(duck.constructor === Bird, "<code>duck.constructor</code> should return <code>Bird</code>.");'
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- text: <code>Dog.prototype</code>应该是<code>Animal</code>一个实例。
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testString: 'assert(Animal.prototype.isPrototypeOf(Dog.prototype), "<code>Dog.prototype</code> should be an instance of <code>Animal</code>.");'
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- text: <code>beagle.constructor</code>应该返回<code>Dog</code> 。
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testString: 'assert(beagle.constructor === Dog, "<code>beagle.constructor</code> should return <code>Dog</code>.");'
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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function Animal() { }
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function Bird() { }
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function Dog() { }
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Bird.prototype = Object.create(Animal.prototype);
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Dog.prototype = Object.create(Animal.prototype);
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// Add your code below this line
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let duck = new Bird();
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let beagle = new Dog();
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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