112 lines
2.3 KiB
Markdown
112 lines
2.3 KiB
Markdown
---
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id: 5cfa550e84205a357704ccb6
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title: 使用解构赋值来获取对象的值
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challengeType: 1
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forumTopicId: 301216
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dashedName: use-destructuring-assignment-to-extract-values-from-objects
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---
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# --description--
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<dfn>解构赋值</dfn>是 ES6 引入的新语法，用来从数组和对象中提取值，并优雅地对变量进行赋值。
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有如下 ES5 代码：
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```js
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const user = { name: 'John Doe', age: 34 };
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const name = user.name;
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const age = user.age;
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```
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`name` 的值应该是字符串 `John Doe`， `age` 的值应该是数字 `34`。
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下面是使用 ES6 解构赋值语句，实现相同效果：
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```js
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const { name, age } = user;
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```
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同样，`name` 的值应该是字符串 `John Doe`， `age` 的值应该是数字 `34`。
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在这里，自动创建 `name` 和 `age` 变量，并将 `user` 对象相应属性的值赋值给它们。 这个方法简洁多了。
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你可以从对象中提取尽可能多或很少的值。
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# --instructions--
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把两个赋值语句替换成效果相同的解构赋值语句。 `today` 和 `tomorrow` 的值应该还是 `HIGH_TEMPERATURES` 对象中 `today` 和 `tomorrow` 属性的值。
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# --hints--
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应该移除 ES5 赋值语句。
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```js
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assert(
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!__helpers
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.removeJSComments(code)
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.match(/today\s*=\s*HIGH_TEMPERATURES\.(today|tomorrow)/g)
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);
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```
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应该使用解构赋值创建 `today` 变量。
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```js
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assert(
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__helpers
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.removeJSComments(code)
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.match(
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/(var|let|const)\s*{\s*(today[^}]*|[^,]*,\s*today)\s*}\s*=\s*HIGH_TEMPERATURES(;|\s+|\/\/)/g
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)
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);
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```
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应该使用解构赋值创建 `tomorrow` 变量。
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```js
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assert(
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__helpers
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.removeJSComments(code)
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.match(
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/(var|let|const)\s*{\s*(tomorrow[^}]*|[^,]*,\s*tomorrow)\s*}\s*=\s*HIGH_TEMPERATURES(;|\s+|\/\/)/g
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)
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);
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```
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`today` 应该等于 `77`，`tomorrow` 应该等于 `80`。
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```js
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assert(today === 77 && tomorrow === 80);
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```
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# --seed--
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## --seed-contents--
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```js
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const HIGH_TEMPERATURES = {
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yesterday: 75,
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today: 77,
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tomorrow: 80
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};
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// Only change code below this line
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const today = HIGH_TEMPERATURES.today;
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const tomorrow = HIGH_TEMPERATURES.tomorrow;
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// Only change code above this line
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```
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# --solutions--
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```js
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const HIGH_TEMPERATURES = {
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yesterday: 75,
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today: 77,
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tomorrow: 80
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};
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const { today, tomorrow } = HIGH_TEMPERATURES;
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```
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