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											2018-10-10 18:03:03 -04:00
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											2021-03-04 09:49:46 -08:00
										 |  |  | title: 使用 delete 关键字删除对象属性 | 
					
						
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											2018-10-10 18:03:03 -04:00
										 |  |  | challengeType: 1 | 
					
						
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										 |  |  | forumTopicId: 301168 | 
					
						
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										 |  |  | dashedName: use-the-delete-keyword-to-remove-object-properties | 
					
						
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											2018-10-10 18:03:03 -04:00
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										 |  |  | # --description--
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										 |  |  | 现在我们已经学习了什么是对象以及对象的基本特性和用途。 总之,对象是以键值对的形式,灵活、直观地存储结构化数据的一种方式,***而且***,通过对象的属性查找属性值是速度很快的操作。 在本章余下的挑战中,我们来了解一下对象的几种常用操作,这样你能更好地在代码中使用这个十分有用的数据结构:对象。 | 
					
						
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											2018-10-10 18:03:03 -04:00
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										 |  |  | 在之前的挑战中,我们已经试过添加和修改对象中的键值对。 现在我们来看看如何从一个对象中*移除*一个键值对。 | 
					
						
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										 |  |  | 我们再来回顾一下上一个挑战中的 `foods` 对象。 如果我们想移除 `apples` 属性,可以像这样使用 `delete` 关键字: | 
					
						
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											2018-10-10 18:03:03 -04:00
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							|  |  |  | ```js | 
					
						
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										 |  |  | delete foods.apples; | 
					
						
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										 |  |  | ``` | 
					
						
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										 |  |  | # --instructions--
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										 |  |  | 请使用 delete 关键字来移除 `foods` 中的 `oranges`、`plums` 和 `strawberries` 属性。 | 
					
						
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										 |  |  | # --hints--
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										 |  |  | `foods` 对象应只包含 3 个属性:`apples`、`grapes` 和 `bananas`。 | 
					
						
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							|  |  |  | ```js | 
					
						
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										 |  |  | assert( | 
					
						
							|  |  |  |   !foods.hasOwnProperty('oranges') && | 
					
						
							|  |  |  |     !foods.hasOwnProperty('plums') && | 
					
						
							|  |  |  |     !foods.hasOwnProperty('strawberries') && | 
					
						
							|  |  |  |     Object.keys(foods).length === 3 | 
					
						
							|  |  |  | ); | 
					
						
							|  |  |  | ``` | 
					
						
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										 |  |  | 应使用 `delete` 关键字来移除 `oranges`、`plums` 和 `strawberries` 属性。 | 
					
						
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										 |  |  | ```js | 
					
						
							|  |  |  | assert( | 
					
						
							|  |  |  |   code.search(/oranges:/) !== -1 && | 
					
						
							|  |  |  |     code.search(/plums:/) !== -1 && | 
					
						
							|  |  |  |     code.search(/strawberries:/) !== -1 | 
					
						
							|  |  |  | ); | 
					
						
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										 |  |  | ``` | 
					
						
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										 |  |  | # --seed--
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							|  |  |  | ## --seed-contents--
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							|  |  |  | ```js | 
					
						
							|  |  |  | let foods = { | 
					
						
							|  |  |  |   apples: 25, | 
					
						
							|  |  |  |   oranges: 32, | 
					
						
							|  |  |  |   plums: 28, | 
					
						
							|  |  |  |   bananas: 13, | 
					
						
							|  |  |  |   grapes: 35, | 
					
						
							|  |  |  |   strawberries: 27 | 
					
						
							|  |  |  | }; | 
					
						
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							|  |  |  | // Only change code below this line | 
					
						
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							|  |  |  | // Only change code above this line | 
					
						
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							|  |  |  | console.log(foods); | 
					
						
							|  |  |  | ``` | 
					
						
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										 |  |  | # --solutions--
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										 |  |  | ```js | 
					
						
							|  |  |  | let foods = { | 
					
						
							|  |  |  |   apples: 25, | 
					
						
							|  |  |  |   oranges: 32, | 
					
						
							|  |  |  |   plums: 28, | 
					
						
							|  |  |  |   bananas: 13, | 
					
						
							|  |  |  |   grapes: 35, | 
					
						
							|  |  |  |   strawberries: 27 | 
					
						
							|  |  |  | }; | 
					
						
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							|  |  |  | delete foods.oranges; | 
					
						
							|  |  |  | delete foods.plums; | 
					
						
							|  |  |  | delete foods.strawberries; | 
					
						
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							|  |  |  | console.log(foods); | 
					
						
							|  |  |  | ``` |