67 lines
2.9 KiB
Markdown
67 lines
2.9 KiB
Markdown
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---
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id: 587d7db1367417b2b2512b88
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title: Override Inherited Methods
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challengeType: 1
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videoUrl: ''
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localeTitle: ''
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---
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## Description
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<section id="description">在前面的课程中，您了解到一个对象可以通过克隆其<code>prototype</code>对象从另一个对象继承其行为（方法）： <blockquote> ChildObject.prototype = Object.create（ParentObject.prototype）; </blockquote>然后， <code>ChildObject</code>通过将它们链接到其<code>prototype</code> <code>ChildObject</code>获得自己的方法： <blockquote> ChildObject.prototype.methodName = function（）{...}; </blockquote>可以覆盖继承的方法。它以相同的方式完成 - 通过使用与要覆盖的方法名称相同的方法名称向<code>ChildObject.prototype</code>添加方法。以下是<code>Bird</code>重写从<code>Animal</code>继承的<code>eat()</code>方法的示例： <blockquote> function Animal（）{} <br> Animal.prototype.eat = function（）{ <br>返回“nom nom nom”; <br> }; <br>函数Bird（）{} <br><br> //继承Animal的所有方法<br> Bird.prototype = Object.create（Animal.prototype）; <br><br> // Bird.eat（）重写Animal.eat（） <br> Bird.prototype.eat = function（）{ <br>返回“peck peck peck”; <br> }; </blockquote>如果你有一个实例，请<code>let duck = new Bird();</code>你调用<code>duck.eat()</code> ，这就是JavaScript在<code>duck's</code> <code>prototype</code>链上寻找方法的方法： <code>duck.eat()</code> =>这里定义了eat（）吗？ No. 2. Bird =>这里定义了eat（）吗？ =>是的。执行它并停止搜索。 3. Animal => eat（）也被定义，但JavaScript在达到此级别之前停止搜索。 4. Object => JavaScript在达到此级别之前停止搜索。 </section>
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## Instructions
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<section id="instructions">覆盖<code>Penguin</code>的<code>fly()</code>方法，使其返回“唉，这是一只不会飞的鸟”。 </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>penguin.fly()</code>应该返回字符串“唉，这是一只不会飞的鸟”。
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testString: 'assert(penguin.fly() === "Alas, this is a flightless bird.", "<code>penguin.fly()</code> should return the string "Alas, this is a flightless bird."");'
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- text: <code>bird.fly()</code>方法应该返回“我正在飞行！”
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testString: 'assert((new Bird()).fly() === "I am flying!", "The <code>bird.fly()</code> method should return "I am flying!"");'
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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 Bird() { }
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Bird.prototype.fly = function() { return "I am flying!"; };
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function Penguin() { }
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Penguin.prototype = Object.create(Bird.prototype);
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Penguin.prototype.constructor = Penguin;
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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 penguin = new Penguin();
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console.log(penguin.fly());
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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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