107 lines
2.2 KiB
Markdown
107 lines
2.2 KiB
Markdown
---
|
||
id: 587d7b89367417b2b2512b4a
|
||
title: 使用解構賦值從嵌套對象中分配變量
|
||
challengeType: 1
|
||
forumTopicId: 301214
|
||
dashedName: use-destructuring-assignment-to-assign-variables-from-nested-objects
|
||
---
|
||
|
||
# --description--
|
||
|
||
你可以使用前兩節課程中相同的原則來解構嵌套對象中的值。
|
||
|
||
使用與前面的例子中類似的對象:
|
||
|
||
```js
|
||
const user = {
|
||
johnDoe: {
|
||
age: 34,
|
||
email: 'johnDoe@freeCodeCamp.com'
|
||
}
|
||
};
|
||
```
|
||
|
||
這是解構對象的屬性值賦值給具有相同名字的變量:
|
||
|
||
```js
|
||
const { johnDoe: { age, email }} = user;
|
||
```
|
||
|
||
這是將對象的屬性值賦值給具有不同名字的變量:
|
||
|
||
```js
|
||
const { johnDoe: { age: userAge, email: userEmail }} = user;
|
||
```
|
||
|
||
# --instructions--
|
||
|
||
將兩個賦值語句替換成等價的解構賦值。 `lowToday` 和 `highToday` 應該爲 `LOCAL_FORECAST` 中 `today.low` 和 `today.high` 的值。
|
||
|
||
# --hints--
|
||
|
||
不能使用 ES5 的賦值語句。
|
||
|
||
```js
|
||
assert(
|
||
!code.match(/lowToday = LOCAL_FORECAST\.today\.low/g) &&
|
||
!code.match(/highToday = LOCAL_FORECAST\.today.high/g)
|
||
);
|
||
```
|
||
|
||
應該使用解構創建 `lowToday` 變量。
|
||
|
||
```js
|
||
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
|
||
)
|
||
);
|
||
```
|
||
|
||
應該使用解構創建 `highToday` 變量。
|
||
|
||
```js
|
||
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
|
||
)
|
||
);
|
||
```
|
||
|
||
`lowToday` 應等於 `64`,`highToday` 應等於 `77`。
|
||
|
||
```js
|
||
assert(lowToday === 64 && highToday === 77);
|
||
```
|
||
|
||
# --seed--
|
||
|
||
## --seed-contents--
|
||
|
||
```js
|
||
const LOCAL_FORECAST = {
|
||
yesterday: { low: 61, high: 75 },
|
||
today: { low: 64, high: 77 },
|
||
tomorrow: { low: 68, high: 80 }
|
||
};
|
||
|
||
// Only change code below this line
|
||
|
||
const lowToday = LOCAL_FORECAST.today.low;
|
||
const highToday = LOCAL_FORECAST.today.high;
|
||
|
||
// Only change code above this line
|
||
```
|
||
|
||
# --solutions--
|
||
|
||
```js
|
||
const LOCAL_FORECAST = {
|
||
yesterday: { low: 61, high: 75 },
|
||
today: { low: 64, high: 77 },
|
||
tomorrow: { low: 68, high: 80 }
|
||
};
|
||
|
||
const { today: { low: lowToday, high: highToday }} = LOCAL_FORECAST;
|
||
```
|