73 lines
3.4 KiB
Markdown
73 lines
3.4 KiB
Markdown
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---
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id: 587d7db1367417b2b2512b87
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title: Add Methods After Inheritance
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challengeType: 1
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videoUrl: ''
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localeTitle: 继承后添加方法
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---
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## Description
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<section id="description">除了继承的方法之外，从<code>supertype</code>构造函数继承其<code>prototype</code>对象的构造函数仍然可以拥有自己的方法。例如， <code>Bird</code>是一个从<code>Animal</code>继承其<code>prototype</code>的构造函数： <blockquote> function Animal（）{} <br> Animal.prototype.eat = function（）{ <br> console.log（“nom nom nom”）; <br> }; <br>函数Bird（）{} <br> Bird.prototype = Object.create（Animal.prototype）; <br> Bird.prototype.constructor = Bird; </blockquote>除了从<code>Animal</code>继承的内容之外，您还希望添加<code>Bird</code>对象独有的行为。在这里， <code>Bird</code>将获得一个<code>fly()</code>函数。函数以与任何构造函数相同的方式添加到<code>Bird's</code> <code>prototype</code> ： <blockquote> Bird.prototype.fly = function（）{ <br> console.log（“我在飞！”）; <br> }; </blockquote>现在<code>Bird</code>实例将同时使用<code>eat()</code>和<code>fly()</code>方法： <blockquote> let duck = new Bird（）; <br> duck.eat（）; //打印“nom nom nom” <br> duck.fly（）; //打印“我在飞！” </blockquote></section>
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## Instructions
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<section id="instructions">添加所有必需的代码，以便<code>Dog</code>对象继承自<code>Animal</code> ， <code>Dog's</code> <code>prototype</code>构造函数设置为Dog。然后将一个<code>bark()</code>方法添加到<code>Dog</code>对象，以便<code>beagle</code>可以<code>eat()</code>和<code>bark()</code> 。 <code>bark()</code>方法应该打印“Woof！”到控制台。 </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>Animal</code>不应该响应<code>bark()</code>方法。
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testString: 'assert(typeof Animal.prototype.bark == "undefined", "<code>Animal</code> should not respond to the <code>bark()</code> method.");'
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- text: <code>Dog</code>应该继承<code>Animal</code>的<code>eat()</code>方法。
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testString: 'assert(typeof Dog.prototype.eat == "function", "<code>Dog</code> should inherit the <code>eat()</code> method from <code>Animal</code>.");'
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- text: <code>Dog</code>应该将<code>bark()</code>方法作为<code>own</code>属性。
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testString: 'assert(Dog.prototype.hasOwnProperty("bark"), "<code>Dog</code> should have the <code>bark()</code> method as an <code>own</code> property.");'
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- text: <code>beagle</code>应该是<code>Animal</code>一个<code>instanceof</code> 。
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testString: 'assert(beagle instanceof Animal, "<code>beagle</code> should be an <code>instanceof</code> <code>Animal</code>.");'
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- text: <code>beagle</code>的构造函数应该设置为<code>Dog</code> 。
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testString: 'assert(beagle.constructor === Dog, "The constructor for <code>beagle</code> should be set to <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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Animal.prototype.eat = function() { console.log("nom nom nom"); };
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function Dog() { }
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// Add your code below this line
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// Add your code above this line
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let beagle = new Dog();
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beagle.eat(); // Should print "nom nom nom"
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beagle.bark(); // Should print "Woof!"
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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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