102 lines
2.1 KiB
Markdown
102 lines
2.1 KiB
Markdown
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---
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id: 5cfa550e84205a357704ccb6
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title: 使用解構賦值來獲取對象的值
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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>解構賦值</dfn>是 ES6 引入的新語法，用來從數組和對象中提取值，並優雅地對變量進行賦值。
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有如下 ES5 代碼：
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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` 的值應該是字符串 `John Doe`， `age` 的值應該是數字 `34`。
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下面是使用 ES6 解構賦值語句，實現相同效果：
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```js
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const { name, age } = user;
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```
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同樣，`name` 的值應該是字符串 `John Doe`， `age` 的值應該是數字 `34`。
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在這裏，自動創建 `name` 和 `age` 變量，並將 `user` 對象相應屬性的值賦值給它們。 這個方法簡潔多了。
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你可以從對象中提取儘可能多或很少的值。
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# --instructions--
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把兩個賦值語句替換成效果相同的解構賦值語句。 `today` 和 `tomorrow` 的值應該還是 `HIGH_TEMPERATURES` 對象中 `today` 和 `tomorrow` 屬性的值。
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# --hints--
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應該移除 ES5 賦值語句。
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```js
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assert(
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!code.match(/today\s*=\s*HIGH_TEMPERATURES\.(today|tomorrow)/g)
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);
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```
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應該使用解構賦值創建 `today` 變量。
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```js
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assert(
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code.match(/(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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應該使用解構賦值創建 `tomorrow` 變量。
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```js
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assert(
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code.match(/(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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`today` 應該等於 `77`，`tomorrow` 應該等於 `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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