77 lines
2.8 KiB
Markdown
77 lines
2.8 KiB
Markdown
|
---
|
|||
|
|
id: 56533eb9ac21ba0edf2244c8
|
|||
|
|
title: Accessing Object Properties with Bracket Notation
|
|||
|
|
challengeType: 1
|
|||
|
|
guideUrl: 'https://chinese.freecodecamp.org/guide/certificates/accessing-objects-properties-with-bracket-notation'
|
|||
|
|
videoUrl: ''
|
|||
|
|
localeTitle: 使用括号表示法访问对象属性
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Description
|
|||
|
|
<section id="description">访问对象属性的第二种方法是括号表示法（ <code>[]</code> ）。如果您尝试访问的对象的属性在其名称中有空格，则需要使用括号表示法。但是，您仍然可以在没有空格的对象属性上使用括号表示法。以下是使用括号表示法读取对象属性的示例： <blockquote> var myObj = { <br> “太空名称”：“柯克”， <br> “更多空间”：“Spock”， <br> “NoSpace”：“USS Enterprise” <br> }; <br> myObj [“空间名称”]; //柯克<br> myObj ['更多空间']; // Spock <br> MyObj中[ “无空间”]; // USS Enterprise </blockquote>请注意，其中包含空格的属性名称必须使用引号（单引号或双引号）。 </section>
|
|||
|
|
|
|||
|
|
## Instructions
|
|||
|
|
<section id="instructions">使用括号表示法<code>testObj</code>属性<code>"an entree"</code> <code>testObj</code> <code>"an entree"</code>和<code>"the drink"</code>的<code>testObj</code> ，并分别将它们分配给<code>entreeValue</code>和<code>drinkValue</code> 。 </section>
|
|||
|
|
|
|||
|
|
## Tests
|
|||
|
|
<section id='tests'>
|
|||
|
|
|
|||
|
|
```yml
|
|||
|
|
tests:
|
|||
|
|
- text: <code>entreeValue</code>应该是一个字符串
|
|||
|
|
testString: 'assert(typeof entreeValue === "string" , "<code>entreeValue</code> should be a string");'
|
|||
|
|
- text: <code>entreeValue</code>的值应该是<code>"hamburger"</code>
|
|||
|
|
testString: 'assert(entreeValue === "hamburger" , "The value of <code>entreeValue</code> should be <code>"hamburger"</code>");'
|
|||
|
|
- text: <code>drinkValue</code>应该是一个字符串
|
|||
|
|
testString: 'assert(typeof drinkValue === "string" , "<code>drinkValue</code> should be a string");'
|
|||
|
|
- text: <code>drinkValue</code>的值应该是<code>"water"</code>
|
|||
|
|
testString: 'assert(drinkValue === "water" , "The value of <code>drinkValue</code> should be <code>"water"</code>");'
|
|||
|
|
- text: 您应该使用括号表示法两次
|
|||
|
|
testString: 'assert(code.match(/testObj\s*?\[("|")[^""]+\1\]/g).length > 1, "You should use bracket notation twice");'
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
</section>
|
|||
|
|
|
|||
|
|
## Challenge Seed
|
|||
|
|
<section id='challengeSeed'>
|
|||
|
|
|
|||
|
|
<div id='js-seed'>
|
|||
|
|
|
|||
|
|
```js
|
|||
|
|
// Setup
|
|||
|
|
var testObj = {
|
|||
|
|
"an entree": "hamburger",
|
|||
|
|
"my side": "veggies",
|
|||
|
|
"the drink": "water"
|
|||
|
|
};
|
|||
|
|
|
|||
|
|
// Only change code below this line
|
|||
|
|
|
|||
|
|
var entreeValue = testObj; // Change this line
|
|||
|
|
var drinkValue = testObj; // Change this line
|
|||
|
|
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
</div>
|
|||
|
|
|
|||
|
|
|
|||
|
|
### After Test
|
|||
|
|
<div id='js-teardown'>
|
|||
|
|
|
|||
|
|
```js
|
|||
|
|
console.info('after the test');
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
</div>
|
|||
|
|
|
|||
|
|
</section>
|
|||
|
|
|
|||
|
|
## Solution
|
|||
|
|
<section id='solution'>
|
|||
|
|
|
|||
|
|
```js
|
|||
|
|
// solution required
|
|||
|
|
```
|
|||
|
|
</section>
|