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104 lines
2.5 KiB
Markdown
104 lines
2.5 KiB
Markdown
---
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id: 587d7b89367417b2b2512b4a
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title: Use Destructuring Assignment to Assign Variables from Nested Objects
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challengeType: 1
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forumTopicId: 301214
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localeTitle: 使用解构赋值从嵌套对象中分配变量
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---
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## Description
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<section id='description'>
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同样，我们可以将 <em>嵌套的对象</em>解构到变量中。
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请看以下代码：
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```js
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const user = {
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johnDoe: {
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age: 34,
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email: 'johnDoe@freeCodeCamp.com'
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}
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};
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```
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这是解构对象的属性并赋值给相同名字的变量：
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```js
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const { johnDoe: { age, email }} = user;
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```
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这是将对象的属性值指定给一个不同的名字：
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```js
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const { johnDoe: { age: userAge, email: userEmail }} = user;
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```
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</section>
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## Instructions
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<section id='instructions'>
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将两个赋值语句替换成等价的解构赋值。<code>lowToday</code> 和 <code>highToday</code> 应该为 <code>LOCAL_FORECAST</code> 中 <code>today.low</code> 和 <code>today.high</code> 的值。
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</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: 不能使用 ES5 的赋值语句。
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testString: assert(!code.match(/lowToday = LOCAL_FORECAST\.today\.low/g) && !code.match(/highToday = LOCAL_FORECAST\.today.high/g))
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- text: 应该使用解构创建 <code>lowToday</code> 变量。
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testString: assert(code.match(/(var|const|let)\s*{\s*today\s*:\s*{\s*(low\s*:\s*lowToday[^}]*|[^,]*,\s*low\s*:\s*lowToday\s*)}\s*}\s*=\s*LOCAL_FORECAST(;|\s+|\/\/)/g));
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- text: 应该使用解构创建 <code>highToday</code> 变量。
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testString: assert(code.match(/(var|const|let)\s*{\s*today\s*:\s*{\s*(high\s*:\s*highToday[^}]*|[^,]*,\s*high\s*:\s*highToday\s*)}\s*}\s*=\s*LOCAL_FORECAST(;|\s+|\/\/)/g));
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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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const LOCAL_FORECAST = {
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yesterday: { low: 61, high: 75 },
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today: { low: 64, high: 77 },
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tomorrow: { low: 68, high: 80 }
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};
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// change code below this line
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const lowToday = LOCAL_FORECAST.today.low;
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const highToday = LOCAL_FORECAST.today.high;
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// change code above this line
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console.log(lowToday); // should be 64
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console.log(highToday); // should be 77
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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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const LOCAL_FORECAST = {
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yesterday: { low: 61, high: 75 },
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today: { low: 64, high: 77 },
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tomorrow: { low: 68, high: 80 }
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};
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// change code below this line
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const { today: { low: lowToday, high: highToday }} = LOCAL_FORECAST;
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// change code above this line
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console.log(highToday); // should be 77
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console.log(highTomorrow); // should be 80
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```
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</section>
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