2018-10-10 18:03:03 -04:00
|
|
|
|
---
|
|
|
|
|
id: 587d7b8b367417b2b2512b53
|
|
|
|
|
title: Use class Syntax to Define a Constructor Function
|
|
|
|
|
challengeType: 1
|
|
|
|
|
videoUrl: ''
|
|
|
|
|
localeTitle: 使用类语法定义构造函数
|
|
|
|
|
---
|
|
|
|
|
|
|
|
|
|
## Description
|
|
|
|
|
<section id="description"> ES6使用关键字<dfn>class</dfn>提供了一种帮助创建对象的新语法。需要注意的是, <code>class</code>语法只是一种语法,而不是面向对象范例的完整的基于类的实现,不像Java,Python或Ruby等语言。在ES5中,我们通常定义一个构造函数function,并使用<code>new</code>关键字实例化一个对象。 <blockquote> var SpaceShuttle = function(targetPlanet){ <br> this.targetPlanet = targetPlanet; <br> } <br> var zeus = new SpaceShuttle('Jupiter'); </blockquote>类语法只是替换构造函数创建: <blockquote> class SpaceShuttle { <br>构造(targetPlanet){ <br> this.targetPlanet = targetPlanet; <br> } <br> } <br> const zeus = new SpaceShuttle('Jupiter'); </blockquote>请注意, <code>class</code>关键字声明了一个新函数,并添加了一个构造函数,该函数将在调用<code>new</code>调用 - 以创建新对象。 </section>
|
|
|
|
|
|
|
|
|
|
## Instructions
|
|
|
|
|
<section id="instructions">使用<code>class</code>关键字并编写适当的构造函数来创建<code>Vegetable</code>类。使用<code>Vegetable</code>可以创建具有属性<code>name</code>的蔬菜对象,以传递给构造函数。 </section>
|
|
|
|
|
|
|
|
|
|
## Tests
|
|
|
|
|
<section id='tests'>
|
|
|
|
|
|
|
|
|
|
```yml
|
|
|
|
|
tests:
|
|
|
|
|
- text: <code>Vegetable</code>应该是一个<code>class</code>具有限定<code>constructor</code>方法。
|
2020-02-18 01:40:55 +09:00
|
|
|
|
testString: assert(typeof Vegetable === 'function' && typeof Vegetable.constructor === 'function');
|
2018-10-10 18:03:03 -04:00
|
|
|
|
- text: <code>class</code>关键字。
|
2020-02-18 01:40:55 +09:00
|
|
|
|
testString: assert(code.match(/class/g));
|
2018-10-10 18:03:03 -04:00
|
|
|
|
- text: <code>Vegetable</code>可以实例化。
|
2020-02-18 01:40:55 +09:00
|
|
|
|
testString: assert(() => {const a = new Vegetable("apple"); return typeof a === 'object';});
|
2018-10-10 18:03:03 -04:00
|
|
|
|
- text: <code>carrot.name</code>应该返回<code>carrot</code> 。
|
2020-02-18 01:40:55 +09:00
|
|
|
|
testString: assert(carrot.name=='carrot');
|
2018-10-10 18:03:03 -04:00
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
</section>
|
|
|
|
|
|
|
|
|
|
## Challenge Seed
|
|
|
|
|
<section id='challengeSeed'>
|
|
|
|
|
|
|
|
|
|
<div id='js-seed'>
|
|
|
|
|
|
|
|
|
|
```js
|
|
|
|
|
function makeClass() {
|
|
|
|
|
"use strict";
|
|
|
|
|
/* Alter code below this line */
|
|
|
|
|
|
|
|
|
|
/* Alter code above this line */
|
|
|
|
|
return Vegetable;
|
|
|
|
|
}
|
|
|
|
|
const Vegetable = makeClass();
|
|
|
|
|
const carrot = new Vegetable('carrot');
|
|
|
|
|
console.log(carrot.name); // => should be 'carrot'
|
|
|
|
|
|
|
|
|
|
```
|
|
|
|
|
|
|
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
</section>
|
|
|
|
|
|
|
|
|
|
## Solution
|
|
|
|
|
<section id='solution'>
|
|
|
|
|
|
|
|
|
|
```js
|
|
|
|
|
// solution required
|
|
|
|
|
```
|
|
|
|
|
</section>
|