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id, title, challengeType, forumTopicId, localeTitle
| id | title | challengeType | forumTopicId | localeTitle |
|---|---|---|---|---|
| 587d7db1367417b2b2512b87 | Add Methods After Inheritance | 1 | 301315 | 继承后添加方法 |
Description
父类继承其原型对象的构造函数除了继承的方法之外，还可以有自己的方法。
请看举例：Bird是一个构造函数，它继承了Animal构造函数的原型：
function Animal() { }
Animal.prototype.eat = function() {
console.log("nom nom nom");
};
function Bird() { }
Bird.prototype = Object.create(Animal.prototype);
Bird.prototype.constructor = Bird;
除了从Animal构造函数继承的行为之外，还需要给Bird对象添加它独有的行为。这里，我们给Bird对象添加一个fly()函数。函数会以一种与其他构造函数相同的方式添加到Bird的原型中：
Bird.prototype.fly = function() {
console.log("I'm flying!");
};
现在Bird的实例中就有了eat()和fly()这两个方法：
let duck = new Bird();
duck.eat(); // prints "nom nom nom"
duck.fly(); // prints "I'm flying!"
Instructions
Dog对象继承Animal构造函数，并且把Dog 原型上的 constructor 属性设置为 Dog。然后给Dog对象添加一个bark()方法，这样的话，beagle将同时拥有eat()和bark()这两个方法。bark()方法中应该输出 "Woof!" 到控制台。
Tests
tests:
- text: <code>Animal</code>应该没有<code>bark()</code>方法。
testString: assert(typeof Animal.prototype.bark == "undefined");
- text: <code>Dog</code>应该继承了<code>Animal</code>构造函数的<code>eat()</code>方法。
testString: assert(typeof Dog.prototype.eat == "function");
- text: <code>Dog</code>应该有一个<code>bark()</code>方法作为<code>自身</code>属性。
testString: assert(Dog.prototype.hasOwnProperty('bark'));
- text: <code>beagle</code>应该是<code>Animal</code>的一个<code>instanceof</code>。
testString: assert(beagle instanceof Animal);
- text: <code>beagle</code>的 constructor 属性应该被设置为<code>Dog</code>。
testString: assert(beagle.constructor === Dog);
Challenge Seed
function Animal() { }
Animal.prototype.eat = function() { console.log("nom nom nom"); };
function Dog() { }
// Add your code below this line
// Add your code above this line
let beagle = new Dog();
beagle.eat(); // Should print "nom nom nom"
beagle.bark(); // Should print "Woof!"
Solution
function Animal() { }
Animal.prototype.eat = function() { console.log("nom nom nom"); };
function Dog() { }
Dog.prototype = Object.create(Animal.prototype);
Dog.prototype.constructor = Dog;
Dog.prototype.bark = function () {
console.log('Woof!');
};
let beagle = new Dog();
beagle.eat();
beagle.bark();